“People don’t understand the impact of ‘beyond compliance’ and what it requires,” said Mark English, as we were discussing Title 24 energy compliance for various types of custom home designs and remodels. “They don’t understand the difficulty of getting even very small additions to comply – and if they have to meet local green building ordinances that require exceeding Title 24 by 15% or more, it’s even more challenging.”

The problem with additions is that you have less to work with if the project doesn’t comply. Small additions are the hardest, and alterations are even worse, because you’re not adding any conditioned area. If it doesn’t qualify for prescriptive (simple but rigid), you have no choice but to do a whole house energy model. And with the energy model method, you have to justify the values used for the rest of the house that’s not being touched, and which may be built to a long-obsolete energy standard. Those existing R-0 walls can cost you.

Local Green Building Requirements Can Differ

Local green building ordinances can vary in very unpredictable ways. Some areas are adopting BuildItGreen’s GreenPoint Rated system, which at a minimum requires 15% over compliance for new construction. That alone means an energy model, since you can’t “exceed” compliance using the prescriptive form. With the simpler prescriptive form it’s very black and white: either you meet every requirement, or you don’t comply – there’s no extra credit in one area to make up for shortfalls in another.

And it’s not just the GreenPoint checklist that the jurisdictions want, either. If a local Building department is using the GreenPoint Rated system, they often want to see the full follow-through, with a third-party rater who checks up on the project all the way through construction. Others are adopting CALGreen optional tiers, which have pretty much the same measures as BuildItGreen, but it’s structured differently – and that can also have an impact. A locality can even adopt a green building ordinance all on its own that doesn’t reference these systems, although that’s less likely than choosing one standard and then piggybacking further requirements on top of it.

For example, Portola Valley has added a sliding scale GreenPoint score where the larger the house, the more GreenPoints it needs. One of our recent Title 24 projects, a new 6,000 square foot house with 40% glazing to floor area, and metal framed windows (less efficient) required 172 GreenPoints, and in order to make that, we needed to get that house to exceed Title 24 by 35%!

At least with that project, we had the whole house design to work with. We got that project early in the design phase, so we could work with the architect to specify better windows, test out the impact of various system efficiencies, and discuss the additional credits of HERS testing with the assurance that it would likely pass all those tests. With additions, you have to perform the same miracles without altering the majority of the building. And you never know what a local green building ordinance may require.

Even Interior Remodels Now Require Title 24 – in Burlingame

Here’s an example that just came up, and is the subject of this case study. One of our recent Title 24 projects, a remodel of a private home in Burlingame, CA, was mainly an interior remodel. Who knew that Burlingame has an expenditure threshold where any construction project costing over $50K now triggers a Title 24 compliance requirement that has to beat the standard by 15%? And a GreenPoint Checklist with a minimum of 50 points? It’s not like they’re even changing the building envelope.

Well, Mark ran this project and it was -174% behind. “It simply couldn’t be done,” he told me. “It was a nice Mid-Century Modern home with lots of glass everywhere, and vintage insulation. Even if we replaced every window and the heating system, we wouldn’t even make the baseline, let alone 15% over.”

The home's existing condition, before the interior remodel which had no impact on the exterior envelope whatsoever, failed Title 24 by an impossible margin. Note that California's energy code assumes a minimum 13 SEER cooling system, whether any cooling is installed or not.

Mark spoke to a Burlingame city Green Building official, who bluntly told him, “You can apply for a hardship exemption, but you’re not likely to get it.” The owner, a medical professional whom we’ll call Dr X, was already committed to making this project happen. This would have crushed the project completely – and for no justifiable reason.

Then, Mark had a brainstorm. He talked the owner into replacing the heating system with top-of-the-line efficient equipment, and then he created two separate reports: a “before” and an “after”. The “after” report was only (only!) -120% under, a 50% improvement! The home didn’t have any cooling system installed, so no help there. Title 24 assumes you have one even if you don’t, and penalizes accordingly.

The owner agreed to upgrade his heating system and got a 50% improvement.

A Happy Outcome

The owner then submitted the two reports to the City, along with a hardship application form – and to everyone’s astonishment, he got his permit. He wrote us a lovely handwritten note:

“Dear Mark,

Many thanks for all your work and suggestions. I turned in your Title 24 analysis and the hardship for with your wording plus additional palaver and got the permit Monday. It would have been a bleak Thanksgiving if I was still in a suspended state. I really appreciate everything you did.

Best,

Dr. X.”

Lessons Learned

What are the lessons to be learned from this exercise, aside from the fact that new regulations can have unanticipated consequences? Here is what we concluded:

1. Don’t assume that additions are easier than whole-house remodels. You have a lot less to work with and fewer opportunities to improve performance.
2. It’s very hard to get an addition to comply on its own.

Be told.

Impact of Poorly Designed Regulations Can Be Catastrophic

Mark English, ever the advocate for both architects and homeowners, put it this way. “You can’t inhibit people from upgrading their homes – it only kills the economy and prevents construction from happening at all. You can’t hold people hostage and force them to rebuild their entire house for some ridiculous bureaucratic rule that no one’s thought through. At the very least, Burlingame should raise that construction threshold to something like $200K, because any interior remodel, even a kitchen and master suite, can easily cost $125K and more – without any changes to the envelope.”

This goes back to one of our earlier articles on QII credits for spray foam – another “gotcha” that almost cost one of our Title 24 projects its compliance in the field – too late in the game to make it up easily through design or construction changes. The way regulatory processes work, the people writing these codes can’t anticipate their impact in the field, unless we bring it to their attention. I sure hope they see this article!

This news flash about a seemingly obscure topic is of immediate importance to all our architect Title 24 clients -and it’s good news for a change. The Quality of Insulation Installation credit is a HERS test that can help design projects to achieve Title 24 energy compliance, and we’ve had a couple of nasty surprises with it in the past.

Apparently, up until around yesterday, the California Energy Commission did not officially recognize the QII test as valid for open-cell spray foam. Our insulation expert James Morshead of SDI Insulation actually sent me an urgent email yesterday with the news, saying:

Today the California Energy Commission stepped out of the 1980′s and into the 1990′s! The 1/2 pound density spray foam QII check list has finally been approved after long delays.

There will be further revisions and refinements but our State has finally caught up in its own way. They have finally acknowledged what the rest of the country has known and what we have known in our area for years; spray foam works whether its closed cell 2 pound density or open cell 1/2 pound density.

Now on to fixing the U-Value tables!

Active lobbying at the CEC is necessary

As usual, James was an endless trove of insider information. Apart from the news itself, the way that this came about was very revealing of the CEC’s  inner working processes. Most of us don’t understand how or why regulations are the way they are, or how agencies like the CEC solicit input from the public. Apparently one must be prepared to show up in Sacramento at multiple hearings, cultivate deep relationships with CEC staff, sift through the raft of proposed changes for the few items that might be relevant to your industry or situation, and be prepared to pounce on proposed changes with a formally structured submittal process. In other words, hire a full-time lobbyist.

A QII teaching case with the New Solar Homes rebate

We’ve run into some issues on the QII test before, where we’d called it out for extra credit on a Title 24 report on a project that was going for the New Solar Homes rebate. The house had to beat Title 24 by 15% to qualify. James Morshead was actually the insulation installer on that job, and clearly remembered how the HERS rater – NOT one of our Green Compliance Plus Affiliates – flatly refused to accept the low-density spray foam. Closed-cell was fine, but open-cell? No way. This was maybe the first time we’d ever used the QII credit, and nobody, including our other HERS raters, could tell us much about this obscure little omission that suddenly threatened the validity of the project’s energy compliance documentation – and the NSHP rebate. There was much tearing of hair and gnashing of teeth all around.

This close-up shows examples of open cell and closed cell spray foam, also known as low-density and high-density foam. Each cell in the high-density foam is closed, making it a better air barrier - which increases its insulating value.

Whys’ this QII change so darned important?

What are the ramifications of this change and how did it come about? “The recognition of open-cell spray foam has been in process for six and a half years,” said James. “We at SDI didn’t know how the CEC process worked. We thought the CEC would be actively looking at the market to incorporate new developments in a proactive way. But they’re not set up to do that. They’re set up to be reactive, influenced by lobbying input from stakeholders in the marketplace.”

He mentioned a long-ago fight between manufacturers of cellulose and fiberglass insulation, each of whom pushed to have their own products recognized as higher efficiency (higher R value) than the other. “That’s normal business. The CEC is a government agency, and that means that they’re encumbered themselves by a lot of regulatory process. They’re restricted by the system themselves. They rely on input from competing parties, and they solicit information by saying, ‘We want your input.’ They rely on the stakeholders to approach them and provide the necessary technical information.”

But presenting this input to the CEC can be an uphill battle. James mentioned meetings that would be cancelled without notice, web site meeting schedules that were not updated to reflect changes or cancellations, and a very skeptical audience. “They’re coming from an analytical and academic standpoint, but they’re NOT in the field.” And that’s the main point of this discussion, is that until the CEC actually went out to see a low-density spray foam installation, they didn’t believe it worked AT ALL. “They were writing regulations without ever having seen it in action.”

James went on to emphasize that he didn’t fault anyone at the CEC, in fact he admired their work and didn’t envy their task. They’re overworked, underfunded, well-intended, and very committed to the overall goals of helping California to achieve greater energy efficiency. They are doing their absolute best within cumbersome bureaucratic processes that they can’t change, either. To get an an idea of how slow the cycles are for code revisions, consider that the current version of the California energy code, the 2008 code, actually didn’t go into effect until 2010. And, some of its provisions weren’t enforced across the board until October of 2011.

Meritage Homes – a study in foam

Then we got on the topic of Meritage Homes, a high-end home developer who was apparently instrumental in adopting and demonstrating the real value of spray foam. Meritage’s Green FAQ page actually talks about the building envelope as separate from the appliances. James told me that Meritage had decided to use 100% spray foam in all its new developments. Their homes weren’t selling, because of the economy of course – not because the homes were bad. Nobody was buying anything, no one could get financing.

“But then, someone convinced them to foam their homes. The first batch was in Houston, TX. And the spray foam was so effective as an insulator that it ended up causing them some problems early on. Suddenly, all the A/C units in the foam-insulated homes were grossly oversized! Short cycling and such. And they had mold problems as well. But they also realized: OMG! this foam works way beyond the calcs!”

Meritage Homes is a high-end home development company that has implemented energy efficient building envelopes as part of the core design.

And that’s where we get back to the CEC, and the California energy code, which has all sorts of tables and appendices with the allowable thermal values that you can use for various types of wall assemblies and insulations: wood frame, metal frame, etc. (They even have an appendix table for straw bales now.) So, even if your insulation is NASA-quality, the CEC’s Joint Appendices might disallow the use of its true performance capabilities when doing home energy calculations. Which isn’t really fair, considering how difficult it’s been to get even ordinary home designs to meet current California energy standards.

The deconstructed home as sales tool

Most of the time, developers will have a few finished-off model homes that prospective buyers can walk through to see what their home will eventually look like once it’s built. But Meritage did something different. They had a model home with cutout walls to show the interior building assemblies, including studs, wiring – and spray foam insulation. “I call it the deconstructed home,” said James.  “People now are smarter, more educated about building and energy efficiency. They want to see what’s inside. And sales took off! It was a totally new way to sell houses. Local building inspectors liked it, too.”

The homes weren’t selling for more money, but they were selling a lot faster – and, to investors, time is money. The quicker you can recover an investment, the less financing costs you have.

By showing a "deconstructed home" rather than the usual finished showcase model, Meritage Homes has educated homebuyers on construction techniques and efficient building envelopes. This image shows a deconstructed Meritage home from one of its San Antonio developments, as shown on housingzone.com.

CEC’s focus on new construction ignores issues for remodels

Then our conversation touched on another issue with the current California energy code, and that is its almost obsessive focus on NEW construction. One goal at the CEC is for all new homes built after 2030 should be Net Zero. But remodels to existing homes also impact the energy grid, and at least in California, remodels right now represent a significant portion of current construction activity. (This is according to James – I haven’t yet found any data specifically comparing either dollars spent or number of projects of each type, in CA).

Sometimes this results in a very artificial situation when we try to show compliance for a remodeling project. It becomes an exercise in hoping that the project qualifies for prescriptive and we don’t have to run an energy model. For example, if a remodel is not adding any square footage, but the total glazing area is over 20% of the floor area, there are situations where the project just doesn’t qualify for prescriptive compliance. And let’s say that this is a low-budget project; they’re changing out the heating system and enlarging a couple of windows and leaving the rest alone, maybe it’s mainly an interior remodel which doesn’t affect the building envelope.

Well, there are times we’ve had to run a whole-building model that included all portions of the existing home that aren’t being upgraded, but which aren’t built to current energy standards. It’s easy to go down a path of adding new energy measures that not only add to the cost of the project, but which can just get ridiculous. Open more existing walls to re-insulate? You could trigger a seismic upgrade. Replace all the windows? Well, maybe the old windows were still perfectly good, why throw them away? Is that “sustainable building”? I’ve spent hours reading the Residential Compliance Manual’s sections on alterations and remodels, and sometimes writing to the CEC, to find out what’s really allowable.

Trying to get a small remodel to pass California Title 24 compliance can be more agonizing than modeling new construction. This vintage contortionist image is from "The Circus, 1870-1950" published by TASCHEN.

QII checklists for each type of insulation didn’t include one for open-cell spray foam

James reminded me that the HERS rater has to follow different QII checklists based on which type of insulation is used in the project. So there’s one QII checklist for fiberglass batt insulation, and a different checklist to use for blown-in, etc. Here’s a nice checklist writeup from ConSol, an energy group based in Stockton.

This checklist does not affect allowable R-values used in the Title 24 performance calculations. All it does is say that insulation should be installed evenly with no air gaps, empty spots, or compression, and that wall cavities should be sealed to limit air flow through permeable insulation types. The extra credit is really a make-up because the assumption is that typical insulation installation procedures are so shoddy that substandard installations are the norm rather than the exception. So, what’s not to like about open-cell spray foam exactly? And yet, because the CEC had no official checklist that was specific to open-cell, and they didn’t want to lump open-cell and closed-cell together, the omission has led many HERS raters to conclude that low-density spray foam was simply not allowed for the QII credit. That may in fact have been the official CEC policy, too.

Some HERS raters have very extensive backgrounds in building efficiency, construction, and green building; others just don’t have the same depth of knowledge. That’s one reason we chose to list some HERS raters on Green Compliance Plus who we felt had a better grasp of the underlying principles behind Title 24 energy compliance. Our HERS rater affiliates are people with multiple credentials: some are HERS and GreenPoint Raters, some also have CEPE certification, and most have other creds ranging from Energy Star to BPI to LEED for Homes. They already have experience working with integrated project teams on custom home projects, and are more proactive about anticipating potential situations ahead of time or recommending solutions instead of just showing up for the inspection and saying, “Well, you fail, and there’s nothing I can do to help. You won’t get your rebate after all. ‘Bye, now.”

The CEC doesn’t always realize these ramifications until they’re pointed out

On the above mentioned NSHP case study, when James brought this up to the CEC staff and engineers, they were appalled. They had never dreamed that their policies would ever lead to a situation like this. The HERS rater had said, rather erroneously, “This product doesn’t work. Therefore, it’s not allowed.” What he really should have said was, “This product doesn’t have an authorized CEC checklist. And it’s still not allowed.”

Checks and balances to prevent cheating are well intentioned, but they can really gum up the works

“The CEC really wants to discourage cheating,” said James. There are certainly more steps to verification now than in the 2005 code. The whole CalCERTS registry process, with online filing of  the tandem forms for the Title 24 energy compliance report, the installation certificates, and then the HERS certificates, is a great idea but a royal pain in the bum. The online workflow is especially agonizing for custom remodel projects. The CalCERTS support folks are very nice and they also have to follow a ton of regulations that attempt to cover every possible home construction scenario; they’ve never had to consider a different workflow for custom homes where an architect is directly involved.

The code update process is complex and unforgiving, not unlike San Francisco’s planning and approvals process.

So – what if someone wants to advocate for, say, a better attention to remodels, or to custom architect-designed homes? You’d better have a full-time staff person on the job. “The process is so cumbersome, with hearings, submittals, and a lot of 45-day language,” said James. (Really it’s just like the SF planning process) “It’s really arcane – miss something and you’re dead.”

Other industries have their own issues to push for in the energy code. “HVAC, energy consultants, builders… there are a few people who practically sleep in their cars down at the SMUD building in Sacramento.”

It helps to establish a good rapport with the CEC staff, who got high marks from James for dedication and responsiveness. “If you know the system really well, you can know which events are important, but you can’t tell just by looking at the CEC site. It’s a labyrinth, and you need a guide. Try to have a relationship with the CEC staff. They can help you get your voice heard.”

Is the Net Zero goal realistic and achievable by 2030?

James thinks that the goal of having all new homes built in California after 2030 be Net Zero Energy is unrealistic, and not the best way to reduce overall building energy use statewide. “NZE should be affordable to more people than it is right now. We should be making it easier for people to comply even as we tighten the standards. It would be better to reduce energy consumption by 40-50% rather than try for some exotic concept like Net Zero. Go for more basic stuff – air sealing, HVAC sizing, more credit for unventilated roof assemblies.”

“Net Zero Energy is a great idea,” he continued. “But in the construction industry, there are so many different kinds of people involved. There are builders large and small, plan checkers, building inspectors, HERS raters, architects, energy consultants… no one knows how to do it right yet when it comes to energy compliance. Right now, this education is being force-fed into the system when people aren’t ready. NZE is such a complex concept, it requires a very integrated approach. If you push it on people too fast, it’ll be a disaster in the implementation.”

I can’t argue with him there.

Just last month, we interviewed the landscape architecture firm Arterra LLP on our sister blog, The Architect’s Take. Kate Stickley and Vera Gates were so much fun that I thought I’d ask them about Living Roofs – not exactly energy compliance, but a “green building” topic nonetheless. Turns out they’ve done several, and as landscape architects, they bring an artistry and a focus on creating a meaningful sense of place… it’s not just a functional piece of “turf” for a corporate building, where no one ever actually goes up there to enjoy it.

What’s the definition of a “living roof” exactly?

A living roof consists of a thin strata of vegetation and soil, contained within the structure of a building roof and integral to it. Similar to a natural ledge, a select variety of plant types can be grown in the strata, creating additional garden space for use or viewing. Industry definitions characterize different types of Living Roofs according to the depth of the soil strata:

Intensive: This is what we think of as roof gardens, where we have access and usable space. Soil is at least 6” deep. These gardens are intended to be viewed and used as gathering spaces and may include hardscape. They are like gardens planted at the ground level. When we do living roofs, this is more our focus than the thin-strata type as mentioned below.

Extensive: Where there is no use or access and the stratum is very thin. Soil is 1”-6” in depth, planting is treated in mass (as in sheets of succulents or grasses). These are not intended for human use. We don’t have much experience with the latter. For now, just note that the reasons for putting a living roof on a private residence might be different, more personal, than the rationale for installing one on a large corporate or public building.

There is a very good book available on living roofs called “Planting Green Roofs and Living Walls“, by Nigel Dunnett and Noel Kingsbury. Hydrotech is the living roof system we typically use, and they used to have a pretty good web site.

This image shows shallow and deep assemblies for living roofs from a single manufacturer (Carlisle).

What are some good residential examples – your favorites?

One project we did, we’ll call it the “Sky Garden” for the sake of our client’s privacy, involved very extensive roof gardens and some vertical living walls as well. Unfortunately we don’t have photos available at this time, but we can describe it a bit. The house is on a steep hillside, leaving very little usable outdoor space. There are several roof areas, all fully usable, including a fire pit, a patio, and a vegetable garden. Part of the roof is heavily shaded, and the other part gets a lot of sun; there are different plantings in each portion to take best advantage of the sun conditions.

Under the planted area, the roof itself has several drainage areas similar to what you might have in an indoor shower. A layer of foam in each drain area acts as a leveler to maintain an even 6″ soil layer throughout. Rainwater runs underneath the foam to the drainage openings. Roof vents and other mechanical features are concealed inside decorative shrouds that relate to the building materials and guardrail.

[See drawing details further down in this article.]

The most interesting part in a way is the water management, something we mentioned in our last discussion with you as well. Our “Sky Garden” project actually uses four sources of water, in a hierarchy that prioritizes water sources: first, grey water. Next, rainwater. Third, well water. Finally, if and only if all other water sources are dry, say during a drought, the roof garden can be irrigated using city water.

Here’s another recent project, a GreenPoint Rated house in Palo Alto, done in collaboration with architect Cathy Schwabe.

This roof garden designed by Cathy Schwabe and Arterra LLP is a good example of what can be done even with a very small space. The GreenPoint Rated home was designed by architect Cathy Schwabe, who notes that she and Arterra worked collaboratively on the design and detailing, with each firm taking the lead in specific areas.

Although we tend to work on projects where the roof garden is fully usable, it’s also possible to create small rooftop gardens just to add visual interest in an urban setting, especially if the view out the window would otherwise be unappealing – bare rooftops or concrete walls, for example.

What are the benefits of having a living roof? Why would you want one?

The greatest benefit of having a living roof is expanded livable and/or visual garden space. For residential design, this is typically why you would want one. There are many additional benefits that may or may not be a factor, depending on the project, program and climate.

Additional benefits can include:

• Great insulation quality for the building. Living roofs help cool the building in summer and retain warmth in winter.
• Increases longevity of the roof system, by protecting the membrane from ultra-violet light and extremes of temperature.
• Decreases heat sink effect on hot sites-most apparent on a neighborhood level, when many roofs are planted.
• Retains and slows water runoff during and after rain storms, releasing it slowly, over a prolonged period of time. This reduces risk of flash flooding in urban areas during heavy rains.
• Increases opportunity for plant life, habitat & wildlife.

Another green roof from Arterra LLP. A well-designed intensive living roof looks almost the same as ground-level landscaping.

Is there any hard data on these claims for energy savings, heat sink reductions, or comfort improvements?

Yes, but I don’t know that off the top of my head. A lot of research in Europe and Canada has been done. [In densely built-up urban settings, a certain percentage of the rooftops might need to be planted in order to achieve a noticeable change in the overall "urban heat island" effect. Even simply making more roofs light-colored instead of black tar can help.]

Can you have a living wall, too? (e.g. plain old invasive-species ivy)

Yes, there are several, naturally clinging vines. There are also structural green wall systems you can attach to a wall, which provide an armature of support for any vines to grow through. They are separate systems and structures that have different plant types, irrigation and details. There are a number of pre-made systems out there: Fyto Wall and  Tournesol VGM Modular Living Wall to name a few, plus the custom hydroponic system pioneered by Patrick Blanc. We have used both Fyto Wall and the Tournesol systems.

Living walls don't have to accommodate human foot traffic, and they can be quite elaborate. I wonder how much work it takes to keep them so neat-looking, though, and whether these walls have built-in access points on the back side, or whether the maintenance is all done via scaffolding. Left to right: Enrique Browne building in Santiago, Chile; Patrick Blanc living wall design; and a living wall design from Mingo Design.

One thing to point out is that living walls are in many ways a completely different animal from a living roof. We could probably write an entire article just about living walls. Different structures are used to hold the plants in place for a living wall than for a roof. The physics of verticality vs. horizontality affects how weight is supported, how water flows down and out, and of course plants grow upwards so they’ll look different growing on a wall than on a flat surface.

Being vertical, living walls can’t capture as much rainfall, and thus require more irrigation. Sometimes, a lot more. You wouldn’t create a living wall to save water! And they don’t help much with slowing down rain runoff, either. However, they can be a great asset in urban areas as a break from all the concrete, where space is at a premium, and you can’t expand horizontally.

Sounds like a living wall would be impossible in a desert, if they need that much watering.

It’s possible to do a living roof with succulents, but yes – a living wall, even an all-succulent one, would need too much water to be a good choice for a desert area.

When are living roofs NOT a good idea?

• On remodels where the existing structural system and waterproofing wasn’t originally designed to support the added weight of a living roof, where the structure has not been designed to take that load, and there is no budget or scope for reinforcing it. You also need a higher level of waterproofing because living roofs have a rim and might need to tolerate standing water if the drains get clogged up.

• If the roof is sloped more than 2:12 pitch. Sloping roofs are more complicated but they can be done, up to that 2:12 pitch.

• If the living roof area is only a small portion of the entire roofing area. Even for new construction, there is an economy of scale. The smaller the living roof, the less cost benefit it provides.

Drainage and overflow detail from one of Arterra LLP's living roof projects. Image courtesy of Design Ecology.

How much does it cost, as compared to a regular roof?

The range is broad. Simple seeded systems might drop down as low as $15 per SF. However something like our Marin project would be closer to $40 per SF. That includes everything except the roof membrane, which is an additional $8-$12 per SF. It can be hard to come up with a hard number for a project, because if the scope of work included extensive groundscaping and the roof garden is only one portion of that, there are economies of scale that can make it difficult to price that same roof garden as a separate entity.

What are the top things an architect should consider when adding a living roof for a home project?

• The living roof should be well integrated, correctly sized, and serve multiple purposes.
• Waterproofing is key and cannot be fudged.
• The living roof should be an element incorporated early in conceptual design. Curb and parapet detailing, structural engineering, and waterproofing are all integral to the design and the look of the overall building.

What might an architect have to do differently on a project with a living roof?

Decide sooner, rather than later. Adding a living roof later in the design process incurs a great additional cost. However, if a living roof is a possibility, it opens up so much opportunity to expand living space out and into the garden, on multiple levels throughout the home. It also provides an opportunity for an interesting visual feature, as seen from key living areas of the home that might otherwise not have an interesting view.

Parapet waterproofing detail from Arterra LLP, from one of their living roof projects. Image courtesy Design Ecology.

What sort of special consultants would you need to create a roof garden, aside from a landscape designer? What about installers?

There are manufactured systems readily available on the market today that provide all the information an installer would need. Typically a waterproofing specialist is involved, as with most roof installations today.

A landscape contractor typically installs the living roof system. They need to coordinate closely with the general contractor, the roofing subcontractor, and the waterproofing consultant, as the waterproof membrane must be covered as soon as possible after it is tested.

The division between the general contractor and landscape contractors’s scopes of work needs to be definite and clean. It’s best if the general contractor is responsible for the structural construction of the roof and the waterproofing. Then a water test can be done. When the membrane is deemed waterproof, the landscape contractor can begin installation of the layers of material, soil and plants.

This living roof example, courtesy of waterproofing experts Neumann Sloat Blanco Architects LLP, is in Marin, CA. NSB designed the waterproofing, drainage, and soil retention system.

The Neumann Sloat project is a good example of a “non-use” application, where you’re not using it as a patio, but you’re making a visual feature out of something that would otherwise just be an ordinary-looking garage roof.

How are living roofs put together? What are the major materials, components and systems?

They are basically a big bathtub, integrally built into the roof and parapet. First, the roof structure is monolithically waterproofed and heavily tested to ensure the waterproof membrane is intact. Then the pre-manufactured living roof soil system is installed. These vary slightly but they basically consist of a root barrier to keep plant roots from penetrating the roof membrane, a soft insulation layer (which protects the membrane), a drainage layer (like an egg crate), and a layer of filter fabric.

Layering of components from bottom to top are as follows:

• Roof deck (wood frame or concrete)
• Waterproofing
• Protection Board
• Drain Mat
• Geotextile/filter fabric
• Irrigation piping
• Soil
• Plants
• Mulch

Closeup of the Neumann Sloat Blanco living roof shown previously. Plantings here don't need mowing, and have mulch in between.

Along the perimeter of the building at the curb or parapet you will need:

• A curb, which must be at designed to be above the top of the soil
• Minimum 6” width of light-weight gravel between curb and soil area, separated by stainless steel edge restraint (Green Roof Solutions is one supplier)

For drainage:

• The roof deck must be sloped to drain underneath the soil layer. The roof design should include at least 2 drains that are waterproofed and hard piped out to the stormwater or rainwater catchment systems.
• The sloping of roof deck affects thickness of the soil profile above, and must be cross-checked with the project’s structural engineer.
• Lightweight foam board can make up depth difference if needed, to control weight.
• Inspection Chambers  (SS, Green Roof Solutions) will be needed at drains and irrigation valves.

Beneath a living roof is a waterproofed roof, with a rim, and adequate drainage. These stainless steel eyebolts will support a soil retention system. Image courtesy Neumann Sloat Blanco.

A specially formulated soil mixture is then brought in, the thickness of which varies. We prefer to work with a minimum of 9″ of soil, going as deep as 18″ in some situations. The medium tends to be very low in organic matter and have crushed lava or small gravel, which gives it enough heft that it won’t blow away.

Plants go in as they would in any garden although they are usually fairly small container stock. The whole thing is then mulched to secure the soil and insulate the plant roots. If hardscape elements, such as paving or decks, are required to be built over the green roof, that can be done in ways similar to how they would be installed onsite for ground-level landscaping. Hardscape features may be specially designed to minimize weight.

Hydrotech supplies most of these layers. You will pay a premium, because the pre-manufactured costs are usually higher than purchasing the same materials elsewhere. For instance, root barriers are used in ground-level landscaping and are a readily available material. However, Hydrotech requires you use all of their component layers in order to warranty their system. Some clients are willing to pay for this just for the peace of mind. However, a sound green roof system is entirely possible to achieve with products other than theirs.

A soil retention system such as this one is essential for living roofs that are on a slope. Image courtesy Neumann Sloat Blanco.

How do you decide what to plant on a living roof?

The living roof is really like a ledge planting. It’s more exposed. You have only a thin stratum of soil, with higher winds and fuller sun exposure than you might find on the ground level. Plants native to ledges and shallow soils often work well. Most grasses work very well. We design each project uniquely, according to site conditions, depth of planting soil, exposure, etc. There are a lot of resources available now to help in identifying plants that have done well on living roofs.

Another shot showing the soil retention system installed on the living roof for Neumann Sloat Blanco's Marin project. A copper parapet cap provides UV and physical protection for the single-ply membrane underneath. It is also more attractive than leaving the membrane exposed. Image courtesy Neumann Sloat Blanco.

Are living roofs heavy? Do you need structural reinforcement?

Yes, absolutely – especially if you’re going to be walking and sitting out there. They are engineered to assume that the drainage may fail and the whole “bath tub” could then fill up with water. The engineering design must be integrated into the overall design for the structure to take this potential condition into account.

What about retrofits or remodels?

It’s possible, depending on engineering. If the retrofit/remodel is being re-engineered anyway, it is a good possibility.

Do living roof projects ever run up against permitting issues or local building codes? There’s no special credit for them in the California energy-efficiency code, I know that, although green building codes such as CALGreen and BuildItGreen’s GreenPoint Rated system do recognize green roofs to some extent.

Building codes always apply, but we have not run up against anything unusual. If the living roof is accessible, it will need to meet codes for guardrails, etc. There are some LEED and BuildItGreen credits for living roofs, depending on multiple factors.

There are some fire departments that have a say on the plant materials used on living roofs. They review the planting as they would a ground-level landscape. Certain fire-prone plants are prohibited. If local fire codes specify highly fire-resistant roofing materials, they will probably be concerned that plant material should be fireproof as well. On one of our projects, the fire department also required that there be a walkable perimeter around the roof in case firefighters needed roof access during an actual emergency.

Here's another living roof in progress series, this one from Arterra LLP. First comes the framing of the roof and parapet.

What about waterproofing?

The waterproofing makes or breaks these systems, and there is simply no cheating this one. The waterproofing must be a monolithic membrane or there will be problems. That said, the technologies available now for waterproof systems are incredible. Hydrotech seems to be an industry leader. They provide several types of membranes as well and the component layers (including soil). Again, you have to use all of their components in order to get their warranty.

Arterra LLP living roof construction series, part 2: waterproofing layer. The waterproofing is the single most important thing to get right on a living roof. No cheating, no fudging, no shortcuts.

What about maintenance? Do owners need to hire a special service?

The garden needs to be irrigated, fertilized and maintained, as with any garden. Drains need to be serviced as with any roof drain. It is a man-made environment, just like any other landscape. But, roof gardens are more sensitive than gardens created on the ground in full-depth soil. While they may not take more man-hours to maintain than ground-level plantings, living roofs do require more frequent monitoring. Getting the irrigation dialed in correctly takes a bit of attention while the plants are growing in. Over time, they will require less time and be on a par with maintenance for ground-based plantings.

Arterra LLP living roof construction series, part 3: plant layout.

How do you keep a living roof healthy?

If you have planted the right plants and set the right irrigation, they will only need periodic fertilization and regular garden maintenance to stay healthy.

What about weather damage?

This can be a factor, of course. All conditions are more severe on a roof, and damage can occur. Wind is probably the greatest concern and affects the plant choices made.

How easy is it to add greywater irrigation?

Technically, it is easy. Building code sees it differently, though, and at this point I doubt you could get this approved in California. If you did, there would be some concern with a buildup of salts in the soil, so at best it would have to be a dual system, to ensure that you could periodically flush out the salts.

This New York City rooftop garden has quite a mix of plantings, including a small patio, flowers, what might be an herb garden, and even some sizable trees.

Are grey water and rainwater systems the same thing?

No! Grey water and rainwater catchment are two completely different things. Grey water is from household use: laundry, showers, and bathroom sinks. You can’t really store it long-term in a big cistern because it’s not as clean as, say, well water. Too many organisms can “bloom” in grey water. The way to think about grey water is that it’s continually replenished. You can use it right away, or same day, for landscape irrigation. If you have a household with a lot of kids, and a lot of laundry, you might generate a significant amount of grey water to make this worthwhile.

Rainwater catchment systems are an attractive idea but they can be expensive. You need a lot of storage tanks. Rainwater storage might cost around $1.50-$2.00 per gallon. Depending on your garden’s water needs, you could be spending tens of thousands of dollars just for the storage tanks.

Tell me more about water budgets. I assume you’d start by factoring in the average annual rainfall.

Yes, that is where you start, but then you have to identify supplemental water sources in case of a shortfall. It’s also dependent on the plantings, the area, and how shaded the roof area is. We do detailed water budgets as part of all our design projects.

Is a living roof just like having another lawn?

It can be, if you plant grass and mow it. All the accompanying maintenance of having a lawn would apply: heavy irrigation, weekly mowing, heavy fertilization and weeding. We don’t recommend it. Most of our plantings are not lawns. If we do incorporate grasses, they are no-mow natives or ornamental grasses.

Japanese architect Terunobu Fujimori has done some intriguing-looking designs that integrate living plants with slate finished walls. I don't know how water-intensive or maintainable they are, but Fujimori is using vegetation as an artistic medium in a way that preserves some of the cleaner lines in the design.

Can you put a living roof in any climate? What would you do different in Tahoe than in Livermore?

Yes, you can have one in any climate. Living roofs have been used extensively and for many years throughout Europe and Canada, so winter climates are fine. We don’t have much experience designing systems for northern climates, so we don’t know how they handle the snow load. We’d guess that it is mainly an engineering question. The main difference would be the plant choices, as those climates are so different.

Are there other design features that could interfere with a living roof? Certain types of roofing assemblies, tilted roofs, skylights, solar panels, vents, mechanical on the roof, etc.

Yes – all of these can interfere with or modify the design of a living roof. All of these factors should be considered as a whole in the early phases of design. Roof vents can be concealed, of course – solar panels would have to fight for space. And, local fire departments may require a walkable perimeter on a roof, which would also take away space from either gardens or solar arrays.

Some of the DIY living roofs look very untidy. I can’t imagine putting them on a Modern house.

Yes, they can be. That’s the old “hippie” look. We can design water-wise gardens that have a very sophisticated look, but don’t require a lot of water. Each living roof is designed to be in character with the rest of the project.

This images is from a web site promoting "Earth Houses" and it's got a sort of untidy, disheveled charm about it. It's probably not the look you'd want for a very minimal, Modern home design. However, it'll help more with slowing rainwater runoff than a very thin, close-mown piece of turf.

How do surrounding shade trees affect living roof design?

If you are fortunate enough to have mature trees high enough to shade the roof, it is a blessing. Shade is great. Typically, there is more of an effect from surrounding buildings casting shade or creating erratic wind patterns. Our “Sky Garden” project had shade from redwoods on once side and bright sun on the rest. It was designed like any other landscape: shade-tolerant plants on the side shaded by the trees, and drought-tolerant sun plants in the open areas.

Are there any cautionary tales worth mentioning?

Our experiences have been very positive. This is a wonderful way to expand livable and visually attractive space in tight urban settings and on properties with limited buildable space on the ground plane. Steep hillside sites are always looking for more area to create flat outdoor spaces, regardless of of the size of the lot.

The 5,000 year old monument of Newgrange in Ireland is a very early example of a "sod roof" with a multi-layered stone construction beneath.

OK, I’m the first to admit that I know next to nothing about water heaters. Aren’t they those white cylinders that live in garages, as far as possible from the kitchen and the shower? Well… yes and no. In our Title 24 work, which is architect-designed custom single-family projects, the water heater is usually the last thing on anyone’s mind. However, on many of our analysis projects, the quickest, cheapest way to comply with California’s stringent energy-efficiency requirements has been to upgrade the water heater – and sometimes, to include a solar hot water credit.

This article explains how to assess water heater efficiency numbers, including the use of a handy lookup database at the California Energy Center’s web site.

California energy compliance calculation shows separate scoring for three main energy areas: heating, cooling, and water heating. A proposed design, here for a custom single-family home, can be behind on both heating and cooling and still make it up with a high-efficiency water heater.

Why’s water heating so important all of a sudden?

Well… if if a project is behind on heating AND cooling, and it’s already maxed out every other trade-off measure, it can sometimes be salvaged by running it with a more efficient water heater, specifically, a tankless. You’ll really feel the pinch if your project needs to exceed Title 24 by 15% or more. This is a basic requirement for almost all of the “beyond compliance” green standards: GreenPoint Rated, CALGreen optional tiers, LEED for Homes, and incentive programs such as the New Solar Homes Partnership. Local California jurisdictions are adopting various forms of these optional tiers, in some cases requiring very high GreenPoint Rated scores for larger homes.

“The equipment you see with values above about 90% are condensing equipment that have great efficiency values but need different installation practices and cost a bunch more,” warns Ken Nittler, creator of the Micropas Title 24 energy modeling software. “The most common equipment we see are small storage water heaters with energy factors of 0.60 or 0.62. On tankless, we see energy factors of 0.82 or so. On tankless condensing units, we see 0.94 energy factors.”

General Compliance Notes

Radiant Heating. Some basic questions that affect water heaters in Title 24 have to do with the heating system: specifically, whether radiant heat is under consideration. When you run a Title 24 calc with radiant heat as the specified heating type, the water heater drives both the Heating and the Water Heating portions of the score. The Heat score is sensitive to the water heater’s Recovery Efficiency, while Water Heating is associated with the water heater’s Energy Factor.

Solar Hot Water. There’s a very substantial credit for solar hot water in Title 24. You’ll need to know the “insolation fraction” which is the portion of total hot water that you expect to receive from solar thermal. A realistic number may be 25-50%, but that depends on how much sunshine the house will actually receive based on weather, site configuration, surrounding buildings and landforms, house footprint and available space for solar thermal panels, shade trees, and the like. Plan on having a supplemental unit such as an indirect storage tank or an additional water heater, since you’ll need hot water at night as well as during the day.

Radiant + Solar Hot Water Combined. If you’re going for radiant and/or solar hot water, you’ll need a mechanical consultant with strong knowledge of the differences among different manufacturers and unit types. For one thing, radiant heating water temperatures may be different from what you’d need for domestic hot water, so if you’re running them off the same unit or the same tank, specialized installation or components may be needed.

No Electric Water Heaters, Please! Fuel source, such as whether the water heater is gas-fired or electric, has a big impact on Title 24 compliance. Even for all-solar homes. There’s a huge penalty for electric resistance – that’s all you need to know for today’s discussion.

What’s the Highest Efficiency Realistically? The technology inside the water heater, such as whether it’s a two-stage condensing system or a hybrid, can have an indirect impact on Title 24 compliance. Sometimes if something’s not passing I’ll just test some of these numbers to see what happens, but eventually the numbers have to be realistic. This is where I asked around a bit to make sure that a water heater with a .95 efficiency was a real animal. It is – for a tankless. Condensing boilers also can have efficiencies as high as .95. There may also be condensing storage water heaters available, probably at a high premium.

Tankless or instant water heaters typically offer higher efficiencies, and thus are an advantage for demonstrating California energy compliance. Their real-world efficiency depends on other factors such as their proximity to the point of use.

Installation Issues. Do yourself a favor and check with your builder and subs before specifying some of the high-efficiency condensing water heaters. “The equipment you see with values above about 90% are condensing equipment that have great efficiency values but need different installation practices and cost a bunch more,” notes Ken Nittler.

Types of Water Heaters

Water Heater vs. Boiler. What’s the difference between a water heater and a boiler?

• Water heaters cost less and operate at a lower temperature. The “small” version, more typically used for small to medium sized residential dwellings, has an input under 75,000 Btu/hour. Large water heaters have an input that is over 75,000 Btu/hour.

• Boilers make scalding hot water, and more of it, typically around 200 degrees Fahrenheit. That’s why it’s called a “boiler”. A boiler is primarily intended for space heating (radiators), rather than making hot water for daily use. However, boilers are less adaptable to making hot water at lower temperatures at the 120 degrees for showers or 120-135 degrees for radiant flooring.

• They use different efficiency measures, and this last point is what’s crucial for Title 24 compliance.

Indirect Storage Tank. This is a separate, insulated storage tank with a heating element that can be used to collect and store hot water from an intermittent source such as solar thermal. It doesn’t actually heat the water up, it just keeps it hot after it’s already warmed by some other means.

Energy Compliance Calculations – Inputs Needed

Title 24 Defaults. About 90% of the time, we run our Title 24 projects using the software program’s built-in default, which is a small storage water heater with an energy factor of .60. This is a safely conservative assumption, since you can only go upwards from here. Within the Title 24 software, it’s the efficiency that seems to matter, rather than the number of units installed. In reality, however, larger homes are likely to have a boiler, or perhaps several different units at different locations.

Example of one of the pre-created sample inputs for the Micropas Title 24 compliance software. The values used here are specific to the water heater product specified, and they can influence whether or not a project meets compliance standards or not.

Efficiency Measures. Although the array of water heating technologies seem to be almost endless, the only thing that matters for energy compliance are these efficiency ratings, and they’re different depending on whether it’s a water heater or a boiler, whether it’s hooked up to a radiant heating system, and for water heaters the Btu input. There’s some confusion of terms here; I’m sticking to the terms as they are used in the Micropas software inputs.

Energy Factor. Used for “small” water heaters under 75,000 Btu/hour. The energy factor (EF) indicates a water heater’s overall energy efficiency based on the amount of hot water produced per unit of fuel consumed over a typical day. It’s a sort of umbrella measure that includes the recovery efficiency and standby loss measures described below, and is expressed as a decimal fraction between 0 and 1. An EF of .60 is average, while one of .80 will yield noticeable improvement in a project’s Title 24 compliance score.

Recovery Efficiency (sometimes called Thermal Efficiency, or AFUE, although they’re not exactly the same thing). Recovery efficiency is for “large” water heaters and boilers that are 75,000 Btu/hour or above. This is a measure of how effectively the unit turns fuel into heat. It is measured as a fraction between 0 and 1, higher being better. This seems to affect compliance score when radiant or hydronic heat is the main heating system.

Miles Hancock says, “Thermal efficiency is a useless number, measuring the unit’s efficiency at boiling water… what’s key is keeping that water hot, which is the standby loss. Standby loss is what kills the energy compliance.”

Standby Loss. Used only for “large” water heaters with a storage tank, this is the percentage of heat loss per hour from the stored water compared to the heat content of the water. In other words, once the water’s hot, how long does it STAY hot? This is measured as a fraction as well, in this case lower being better. The software built-in for the sample large water heater shows a standby loss of 0.03. Miles

Internal and External Insulation R-Value. Used for indirect storage tanks only. I haven’t tested the effect that this would have on residential compliance, because indirect storage tanks aren’t as common a configuration for the custom home projects that we analyze.

One thing that doesn't affect energy compliance is the style of the faucet - only what's behind it.

Other Inputs. There are additional inputs for heating element type (gas, electric, heat pump), rated input for gas heaters in Btu/hour, storage tank volume in gallons, distribution type, and for some types of water heaters, pilot light size in Btu/hour. For almost all our projects, the fuel type is always gas, since electric water heaters are discouraged.

The distribution type has to do with the piping configuration, and that’s mainly for larger residential projects. Example values are “standard” (the default), “Point of use”, or various recirculating on-demand varieties. I’ve occasionally run projects with these different distribution types to see what difference it made, and for a typical 4,000 SF single-family residential house, it made almost no difference in the compliance score. Sometimes it can make a big difference in the real world, though, so if you or your client are trying to maximize actual energy efficiency, as opposed to just complying with Title 24, try reading up on it in Ann Edminster’s book “Energy Free”.

Heater/Boiler Systems in the Title 24 Software Model. This is based on Micropas, which is one of two programs you can use for California energy compliance. I haven’t used Energy Pro as much, and it’s organized a bit differently. Here are a few basic types of heater/boiler systems that are set up as default or example entries in Micropas (and why you would pick one or the other):

• Small Storage. 40,000 Btu, 50 gallons, 0.60 EF. Use for legacy systems or if you don’t know what else to specify, and you want to assume the lowest allowable efficiency for the time being.
• Large Storage. 100,000 Btu, 100 gallons, 0.77 RE, Standby loss 0.03. Realistically this would be used for a larger home. However, I have noticed that specifying a large storage as opposed to small one lowers the compliance rating, probably because of the higher input rating.
• Tankless (instant). 195,000 Btu, EF .80, RE .76. This is the equivalent to a small storage water heater, and would be used in comparable applications such as a single family home as a more energy-efficient alternative. Compliance advantage is that it’ll boost the water heating portion of the score by as much as 30%, and it’s often a good choice in the real world as well. Real-world advantages: higher efficiency, theoretically endless hot water supply, smaller footprint. Real-world disadvantages: must be located close to point of delivery in order to realize energy savings.
• Boiler. 250,000 Btu, RE .80.
• Instantaneous boiler. 250,000 Btu, RE .80. Same as a boiler, but without a storage tank.
• Electric Storage. This is an electric resistance water heater. You will never, ever, want to use this type when using the performance method of compliance. Occasionally, if you’re trying to grandfather in some unpermitted basement addition, guest cottage, or in-law unit, and the space qualifies for prescriptive (not too much glazing!) you might be able to get away with stating “existing systems to remain” and bypass the issue. But that’s about it.
• Electric Heat Pump. I’ve never had to model this type of water heater, so I can’t speak to it. I don’t think the penalty is as steep for this type as for the electric storage.

Hot Water for Additions. If we run an addition as “Addition Alone”, water heating is not calculated. However, if the addition won’t pass by itself and we have to model the whole house, then the water heater becomes a potential source of energy trade-off. It’s even more important for additions and partial remodels, because other interventions such as upping all the wall insulation may not be available with projects of limited scope.

Pools and Spas. These are not included in the energy report calculations. There are separate energy standards that apply to them. For now, they are outside the scope of this article.

A Nifty Search Lookup for Current Models

Miles Hancock, one of our Green Compliance Plus Affiliates, walked me through the Appliance Efficiency search database on the California Energy Center’s web site. This database contains listings for all appliances certified to the California Energy Commission as meeting currently applicable efficiency standards – so it won’t be of much use for legacy systems (for remodels or additions). Some of the terms they use for efficiency are different from what’s described in the preceding article, but I’ve tried to list their equivalents above, where possible.

The California Energy Center's Appliance Efficiency search database lets you find the rated efficiencies of all models that meet current energy standards.

As most of our readers now know, California’s energy code got a lot stricter in January of 2010. Increasingly, HERS tests are required to comply, even for custom residential projects. HERS tests are special third-party field inspections for things like ductwork, insulation, and air-conditioner efficiency. These tests are called out on the Title 24 energy compliance report, also known as the CF-1R. This energy report must be included on all Building Department submittals statewide throughout California to obtain a building permit. The energy report is then reviewed as part of the plan check process.

And now, a new requirement, or really an old one that’s just now being enforced: All CF-1R reports that call for a HERS test must be officially “registered”. Don’t say we didn’t warn you. Plan checkers are starting to kick back custom residential submittals if they don’t see a CalCERTS watermark on the energy report.

But first, a little background.

Our clients are other design-oriented (read: “modern”) architects. Some of them like to use dramatic walls of glazing in their designs. This, while awesome, presents an energy problem, because glass is a poor insulator compared to, say, a 2×6 framed wall cavity packed with high-performing insulation. California’s energy code seeks to discourage over-glazing by imposing a maximum glazing threshold at 20% of the conditioned floor area.

The Title 24 prescriptive energy report, showing where various HERS tests can be called out. This example is the CF-1R-ADD form for Additions. Title 24 is a reference to California's energy code.

The only way around this is to employ a complex “performance approach” to energy compliance, whereby the project is run through energy modeling software that allows trade-offs – acres of picture windows in exchange for beyond-code energy upgrades elsewhere. As long as the house as a whole is under the threshold for energy usage, the designer can creatively determine how that goal is achieved.

For the performance method of Title 24 energy compliance, the energy modeling software shows whether HERS tests are required on the report's summary page. This example output is from Micropas, a software package that is one of only two authorized packages for demonstrating California energy compliance. As you can see, the project is barely passing even with the additional HERS credit.

For Those Who Came In Late

What are HERS tests?

HERS stands for Home Energy Rating System, a method of diagnostic analysis to determine a home’s energy efficiency by establishing a benchmark and then making site-specific upgrade recommendations for the homeowner. It’s not specific to California; other state energy codes sometimes reference HERS as a standard or its later incarnation, HERS II. HERS raters are independent contractors who are trained and certified through an organization such as CalCERTS.

Why does California’s energy code include HERS testing?

HERS is a recognized and proven standard that relies on empirical testing on a case-by-case basis. Many of the HERS tests address well-known construction deficiencies that can waste up to 30% of a home’s total energy consumption. With a goal of having all new homes statewide be Net Zero by 2030, the State of California has employed a phased approach that tightens the energy code in three-year increments.

When does California require HERS testing?

Depends which energy compliance method you use. Prescriptive requires certain tests, like the duct blaster test, for any new construction or any time a forced-air system is replaced. Performance has this as an option, because it boosts the score quite substantially.

What is this magic database up in the sky, and why haven’t I heard of it before?

Actually, you have if you’ve been reading our blog. But, if you read our blog, chances are your’e the last group of architects to be affected by it. Back in 2009 I took a CABEC-sponsored Title 24 class in Sacramento on upcoming code chances. However, at that time nothing had been implemented, and no one knew how it would actually work.

Since then, CalCERTS has been working with the California Energy Commission to get this up and running. It’s been gradually phased in for different types of projects: mainly production homes, which are far more numerous than the custom, one-off projects and remodels that comprise our own design focus.

The CalCERTS online registry tracks the CF-1R energy compliance reports that require HERS testing. This example is for a residential project.

As an aside, I found the CalCERTS online registry to be very fast, with no glitches – the test project I did in order to write up this article worked just fine. The registry actually parses the report file (a special un-readable ZIP file generated by the energy modeling software) so it “knows” what the project requirements are. The CalCERTS folks themselves were very courteous, helpful, and responsive. I was very impressed that the entire online interface was implemented by one person, who seems to have taken every last aspect of the energy compliance process into account. There oughta be a medal for that!

Why do we need a database? Isn’t there enough red tape as it is?

The idea behind the registry is to reduce cheating. Prior to this, any CF-1R requiring a HERS test had no follow-up to ensure that the test was actually performed, or that the project actually passed the test.

To discourage cheating, CalCERTS registry requires a special output file. It then creates a readable PDF file with the CalCERTS "watermark" applied behind. It also adds a footer to the report with a registration number. This example shows how the watermark is applied to an energy performance report.

So, Who Does What?

Here’s a magic molecule diagram that shows the “new” process highlighted.

Custom residential projects that require HERS testing must now register online with CalCERTS to show compliance with California's energy code.

Green Compliance Plus clients: We take care of pretty much everything that’s in the shaded box. The only thing you’ll need to do is make sure that if your Title 24 energy report calls for any HERS tests, you’ll need the watermarked version on your submittal package.

Note that this diagram only goes up to permitting – there’s a Part II that shows how all the installation certificates and HERS test results are uploaded later down the road. For now, suffice it to say that whatever’s in that energy report has to be followed in the field, because if something doesn’t match up, chances are either the HERS rater or the building inspector will pick up on it.

Impact of Design Changes and Field Swaps

All this bureaucracy means that any changes to the design, including field swaps, could mean having to re-do the energy compliance report and a whole slew of headaches for architect, builder, and owner alike. The energy-modeling “performance” method that we use most of the time allows you to specify the exact efficiencies of every piece of heating equipment and every single window. This allows for a lot of flexibility but it also locks you in to using products that meet those numbers – and are field labeled as such.

Here are just a few of the changes that could trigger a new round of energy analysis: changes to unit models for heating, cooling, or water heating equipment, especially efficiency; any change to the building envelope, including wall and roof assemblies; moving to a less efficient window product; failing a required HERS test; local building requirements that mandate exceeding Title 24 by a specified percentage.

Re-doing the energy report means you try to make up the shortfall somewhere else. This gets harder to do the further along the project is in construction. If you get caught during a site inspection, the damage control can eat up the project budget, not to mention irritating YOUR clients – the homeowners who rely on you, the architect, to guide the project smoothly to completion.

Don’t paint yourself into a corner. Make sure that your builder and all the builder’s subs REALLY understand what’s on that energy report.

All This Applies to Remodels, Too

Even alterations, additions, and other remodeling efforts within the State of California may be subject to this CalCERTS registry requirement. Oftentimes, these are our toughest energy compliance projects, because the scope is limited but for one reason or another we can’t use the simpler prescriptive approach. Usually it’s because the project is over the glazing limit. However, we don’t have much room for energy trade-offs using the energy model because most of the house isn’t being opened or altered.

Every so often at the AIA-San Francisco Small Firms group, we debate amongst ourselves whether getting our residential projects LEED certified is worth the effort. For most of us, with one-off custom residential new homes or remodels, the answer is no – too cumbersome and expensive. If someone is just looking for “green certification” for a California home project, the GreenPoint Rated system from BuildItGreen is a lot more flexible and user-friendly. However, there are a few architects who’ve really made a big push towards LEED certification on some of their homes. So, what are they getting out of it? How do you decide whether to go for GreenPoints or LEED, and what needs to happen with LEED for the process to go smoothly?

(Home shown above is designed by Sparano + Moody Architecture, and has earned LEED Silver certification. But LEED homes don’t all have to be in the wilderness, either.)

The Questionnaire

I took a straw poll amongst our design colleagues, one of our GreenPoint Rater affiliates, and also reached out to a few people that we don’t know – architects, builders, and developers – who’ve completed LEED-certified private homes in California. The questions were, more or less:

• Was it worth the effort?
• What did YOU get out of it?
• Did it add value to the property?
• How much did the rating process itself cost?
• What other additional costs were incurred?
• What can architects, builders, and homeowners do to make the LEED process go more smoothly?

We also discussed the relative merits of LEED vs GreenPoint Rated for private homes in California, including when to go for one vs. the other.

The Respondents

Numerous people took the time to share their opinions freely. In no particular order:

• Rob Lehman of Green Score Solutions. Rob has multiple credentials as a GreenPoint Rater, a HERS rater, and LEED AP, and he’s listed on our Green Compliance Plus affiliates page.

• Rich Williams of ArtHaus, LLC, a residential development company near San Diego. ArtHaus specializes in building sustainable high-end modern homes, and their goal is for all their projects to obtain LEED certification.

• Jonathan Feldman of Feldman Architecture. We’ve known Jonathan for years through the Small Firms Committee – he’s completed or is working on six LEED Platinum and two LEED Gold custom residences. He is a strong proponent of the LEED system.

• Dan Johnson of Arkin Tilt, a well-down Berkeley firm that is in the vanguard of sustainable residential design.

• Eco-Struction, a green builder in Ben Lomond, CA near Santa Cruz.

• Ann V. Edminster, home energy/green building consultant and author of the book “Energy Free” which we reviewed a few months back. She didn’t actually comment for this article, but she’s consulted extensively on LEED projects large and small, including helping design teams set priorities, analyze financial impacts, conduct contractor briefings, and prepare LEED compliance documentation. If you’re looking for a feasibility analysis to help decide whether or not to go for LEED, she might be a good place to start.

LEED and the Building Industry

It’s not just architects who care about it. Builders, developers, homeowners, and home energy consultants all have their own perspectives. Half of the private residences listed as LEED Platinum in California seemed to be credited to developers, builders, or design/build firms rather than architects. However, the majority of the LEED Platinum certified projects were large-scale enterprises like the California Academy of Sciences, multifamily housing, or public buildings – not private residences.

Developers Can Have Ideals, Too

Developers and production builders in general have a public image that seems to view them all as solely focused on making a quick buck. If there weren’t mandatory inspections and statewide energy codes like Title 24, the argument goes, they’d cut every corner, slap the homes together as fast as they can, and get the heck out before the homes started falling over. And if there weren’t environmental protections in place, these same profits-before-people villains would pave over every national park and fill them up with cheap condominiums.

Well, it seems that there’s more variety among people calling themselves “developers” than the stereotypes would suggest. I was surprised to see that around half of the LEED Platinum Homes in California were credited to either developers or design/build firms (developers who turn out a few homes at a time). And not all developers focus on tract homes, either.

One of our own projects from Mark English Architects, the Pepper Drive residence, is a GreenPoint Rated spec home built by a developer that earned a score of 113. Photo: Norma Lopez Molina

Project Scale is a Determinant

“LEED was developed more for production builders than for one-off projects. For one-off projects, GreenPoint Rating is more user-friendly and adaptable,” says Rich Williams of ArtHaus. “However, LEED certification confers a certain amount of prestige, and it’s got more brand awareness than, say GreenPoint Rating. A LEED Platinum certification means it’s the best you can get,” he continued. “A GreenPoint score of 220 is a great score, but people don’t really know what that means yet.”

This new home from residential developer ArtHaus is LEED Platinum certified. Their goal is to have every home they do be LEED certified. Photo: Ramona d'Viola - Ilumus Photography

It’s not just scale, but scope that’s important. LEED for Homes has some prerequisites that may involve a total gut rehab – opening and inspecting every wall and ceiling cavity. So you’d better already have planned on doing a thorough job on any remodel – including a thorough review of any existing HVAC and water heating systems. At least with a home that’s new from the ground up, there are no legacy components to worry about.

Sufficient scope also implies that there is sufficient budget: not only for the measures, but for the certification fees and the extra paperwork. I wasn’t able to get anyone to commit to a dollar amount for the owner’s construction budget as some sort of threshold to determine if LEED would be worthwhile on a particular project. But, the owner and architect should be prepared for upgrades to products, materials, components, systems, and installation procedures where needed to meet requirements – including baselines for energy efficiency. It’s not always something you can tack on later, either – you can insulate now, but even if the insulation is inspected during construction while the walls are open, if it’s not inspected by a LEED certified “Green Rater” – then you may not be able to claim the credit.

Why Did You Choose LEED?

Jonathan Feldman is one residential architect who’s worked on several LEED certified homes, including the award-winning Caterpillar House, a Carmel residence. Based on my conversation with him, the benefits he sees in LEED are:

• A structured and rigorous process
• Verified materials and products
• Tested and calibrated performance
• Process that is raising public awareness

“On our first LEED project, the client came to us very committed to sustainability. She felt that it was reckless the way the building industry largely ignores the devastating impact that it has on our environment,” said Jonathan Feldman of Feldman Architecture. “We were forced to take a wider and more thorough look at different areas of sustainable design, and LEED forced us to follow through with our early project commitments, and also to keep our clients, vendors, and builders committed. We received considerable goodwill from building departments, homeowners associations, and from the press because our project was the first LEED Platinum project in the area. The owners got a house where all the materials, products, and environmental strategies were more carefully considered, specified, installed, calibrated, and tested.”

The Caterpillar House by Feldman Architecture is LEED Platinum certified. Photo: Joe Fletcher

Quality control is an emphasis shared by both GreenPoints and LEED – in fact, any green building standard has to consider both construction quality and overall durability. What’s the point in building something that’s going to be torn down in a few years? Better to build it right the first time, and make it something worth keeping around.

Feldman warned that there was a steep learning curve on his first LEED project, but feels that it’s worth it – if it leads to a much-needed sea change in the building industry. “The more architects and builders go through the process, the easier it becomes. I also think that the more architects and builders share what they learn with each other, the easier it will be for all of us. There are those who don’t want to share what they’ve learned with those whom they view as their competition. I find this amazing. If we are truly concerned with making a dent in curbing the devastating effects of the building industry, then we really should be doing everything we can to help every building project move towards greater sustainability.”

Rich Williams from ArtHaus does it out of personal conviction. “LEED for Homes is a goal that I set for myself. I build stuff that I would want to live in. And with a spec home, LEED certification is a recognition of a benchmark. The biggest take-away from my experience building LEED and GreenPoint Rated homes is that we aren’t really ‘building green’, we are really building to a much higher standard of quality. Consumers will know, because of third-party verification, that the home that they will be living in should be more durable, should require less maintenance, should cost them a lot less to operate, should be more comfortable for them to live in, and (the most important one) should be WAY healthier to live in than other homes that are not being built to these standards. As the Mastercard commercials say, that last one is ‘priceless’. You folks understand how to build a better home, but a lot of folks out there don’t, so having these rating systems in place to provide guidance for doing so is extremely valuable, in my estimation.”

The value of having a structured process with some rigor to it was emphasized by several respondents, as a benefit to both GreenPoints and LEED. LEED might be considered as the stricter of the two, because unlike GPR, the bar to initial certification is a lot higher. Even an “average” home can get a GreenPoint score of 75 without too much effort, but to be LEED certified the home must meet a much larger list of mandatory measures.

Incentives

Rob Lehman reminded me that GreenPoint Rated homes are eligible for additional incentives under California rebate programs such as the New Solar Homes Partnership and California Advanced Homes. If the home is a total gut rehab with all new systems, it may qualify for these programs as “new construction”. So if the client is already thinking about going solar, the rebates can be substantial – and they’re bigger if the home is GreenPoint Rated.

So does that mean that NSHP and CAH ignore LEED certified homes? Not at all. California Advanced Homes rewards it, at least.

• In CAH, there’s a 10% bonus for “Green Home Certification” by a “recognized green building program” and there’s a 15% bonus if the home is 10% smaller than the LEED for Homes size threshold. Yep, LEED has something called Home Size Adjuster which penalizes larger homes.

• NSHP doesn’t appear to reference any green building certifications, although it does mandate energy efficiency. Why? My guess: NSHP is solely about solar power, and reducing home energy use has a direct impact on the PV system size, whereas using low-VOC materials has no impact on the solar array. Both programs use Title 24 as a yardstick – you have to beat Title 24 by 15% or more.

How Much Does LEED for Homes Cost to Do?

How much does it cost? GreenPoint Rating fees seem to be lower than those LEED certification, although I don’t have hard data to do a good fee comparison. Here are a few price points:

• Word of mouth on the street is that it costs $15,000 to get a private residential project LEED certified.

• Rich Williams quoted a fee of $5,000 for getting a 3,000 SF home LEED certified – that’s what it’s costing him – he didn’t include construction costs, though.

• Jonathan Feldman was a bit more specific: estimated rating cost of $5,000 – $10,000 in fees, required advisors, and testers, and another $8,000 – $12,000 for construction practices, materials, research, and design time. “Less in the cases where the clients manage the process themselves,” he added.

Cost analysis can be tricky, because some of it might be things you were planning to do anyway. And with something like LEED, which references other building standards such as Energy Star and (in California) Title 24 energy compliance, assigning weighted costs to requirements can be difficult. Some costs could be incurred during the energy analysis, which is required by both GreenPoints and LEED. In California, projects must exceed Title 24 energy efficiency standards by 15% or more. And, sometimes to get this, a particular project might need upgraded windows, more insulation, higher efficiency systems, or other measures. If you weren’t planning to do these things before, then yes – they’re additional. If you’re just going for the label, that might not be a good reason by itself to go for LEED – or any green certification beyond what local building authorities may require.

“Don’t do it just for the label,” warns Jonathan Feldman. “It’s asinine to jump through that many hoops just for a label. Do the measures because you were going to do them anyway.”

Commercial projects can cost a lot more. Rob Lehman mentioned a LEED certified multifamily project in San Jose with 90 units that cost $90,000 for the LEED certification! “There aren’t that many LEED Green Raters available and they’re expensive,” he noted. I don’t know how this broke out – I’m guessing it likely included the rating, the documentation, and the additional construction costs all rolled into one. And, for a large project like that, having the entire building LEED certified could boost sales and/or rental rates, “especially in certain areas,” he noted.

Does It Add Value to the Property?

Does LEED certification add value to the home? Depending on how you define “value”, here are a few possible definitions:

• A premium that homebuyers are willing to pay, as demonstrated by home sale data
• What realtors and listing services believe are the features that people care about
• What lenders are willing to finance when doing their value assessments of a sale property
• Something that brings the homeowner long-lasting satisfaction, comfort, and enjoyment

The problem is, we don’t really know how much value green building adds to single-family residences, because home listings don’t track green certifications of any kind. So, if a home sells for more, or sells faster, how do we even know whether “green” had anything to do with it? And how can we compare the value of a GreenPoint Rated home vs. a LEED certified one vs. an unrated home that nonetheless has the same green features as a rated one? Thus, data is anecdotal at best.

It seems that the general public is a lot more savvy about Blue Book car values than they are about their own homes. To the extent that they think about it at all, they’re likely to go for spot fixes based on a one-size-fits-all rumor like “I hear that radiant barriers are cool” instead of taking a wholistic approach. A minority of homeowners are DIY energy nerds, who cheerfully experiment on their own homes and report the results, successful or not, for the sake of knowledge sharing alone.

“The MLS real estate listing service does not yet include third-party verifications for any green building programs, so it’s hard to tell exactly how much more the same home would sell for – or how quickly,” said Rich. Rich cited a Portland study claiming an 18% premium, although he personally thinks that 10% is a more reasonable assumption to make. “People want a green home, but they don’t want to pay more for it,” he added. Sometimes green homes sell more quickly, which can be a big advantage to those looking to recoup their investment.

The value of the LEED brand was discussed. A GreenPoint Rated home can have a score anywhere from around 50 to 300 points – but GreenPoint Rating is only within the State of California. LEED has better nationwide brand recognition, and its three designations – Silver, Gold, and Platinum – are simpler to understand, even if the process to achieve them isn’t.

I’d also hazard a guess that homeowners who’ve actually been through the process or who have chosen to invest in the purchase of a LEED certified or GreenPoint Rated home are likely to be happier and more satisfied with their homes than people who are just looking for something affordable. “Most people hate their homes,” was the astonishing opinion of one HVAC engineer whom I met at a Title 24 class last fall. “If they spend any money on improvements, they want it to be something they can see, like a granite countertop.” Both LEED and GreenPoints are intended to create a home that is more comfortable to live in – less drafty, less noisy, and with better indoor air quality – and I’d guess that many people assume that a high level of comfort and control is out of reach, so they just learn to live with whatever they’ve already got.

Don’t Forget: Factor In Energy Savings

Lower operating costs should be factored in to the value equation as well, particularly energy savings. Both LEED and GreenPoints mandate energy-efficient homes – and they both give points beyond the minimum of 15% over “standard” (Title 24 in the case of California). The exact amount of savings will vary by project, and of course if you invest in renewable energy as well as energy retrofitting, the savings will increase. Don’t forget to factor in sudden utility price increases, not that those ever happen… right, Gray Davis?

It could be argued that one can build energy-efficient homes without getting them LEED certified or GreenPoint Rated. However, having a committed process to enforce a level of structure and rigor throughout the project can help guide decision-making and keep the team focused on the right goals. This is one point Ann Edminster makes in her book “Energy Free” – think about why you’re doing it and what your general strategy will be upfront, and then use it as a road map later on.

The other argument – namely that LEED certified buildings aren’t really more energy-efficient – seems to be based on outmoded assumptions. After reviewing the LEED for Homes criteria that include, among other things, requirements for demonstrated overall energy-efficiency (using the HERS index or, in California, beating the Title 24 energy code by 15%), and Energy Star rating, I don’t think it’s possible to go through all that and NOT have a more efficient building. There’s a whole other set of arguments on the counter-effect of efficient buildings actually encouraging more usage – but that topic will have to wait for another day.

Isn’t LEED for Homes Too Cumbersome?

The main critique of LEED for Homes, especially compared to GreenPoint Rating, is that LEED is cumbersome and inflexible. Why would anyone bother when they could just get the project GreenPoint Rated instead? That’s the California voluntary green building standard from BuildItGreen and it’s being adopted by many jurisdictions as a local requirement anyway.

I put this question out to one of our Green Compliance Plus affiliates, Rob Lehman. Rob said “I’d take GreenPoint Rated over LEED for Homes any day” and mentioned the following items:

• GreenPoint Rating is more practical, user-friendly, and affordable. There are a few mandatory measures and the rest are items you pick a la carte. So it can be less stringent but that’s up to you, how many measures you want to include in the project. Because the barrier to entry is lower, it’s actually more of an incentive to get owners to agree to go through the process. Most California jurisdictions that require GreenPoint Rating have reasonable score requirements, at least for now.

• GreenPoint certification is faster and everything goes through the GreenPoint Rater. The LEED application has to go through review in the D.C. headquarters of US Green Building Council and that alone can take up to a year. The USGBC doesn’t respond to questions that quickly, either.

• LEED is very strict and the process is bureaucratic and inflexible. You have to first get your “scenario” approved (by the D.C. central office) and then if you change anything later on, you have to get those changes formally approved as well. Rich Williams added another piece here. “LEED updates can be hard to figure out. Some of them apply retroactively to past projects, some only to projects done in certain years. But what do you expect from an organization that’s based in Washington, D.C.?”

• The LEED mandatory measures are costly. One example that Rob Lehman cited: LEED requires Energy Star certification, which has an extremely stringent quality of insulation inspection – a lot stricter even than the HERS QII credit. It involves a lot of extra sheet rock, building of chases, and even more site visits than a HERS QII inspection.

Rich Williams actually disagreed about LEED being too cumbersome. “Achieving a basic level of LEED is not that difficult,” he said. “It’s like riding a bike – really hard the first time, but then it quickly becomes second nature.” He sees the main challenge as one of training the production builders to be aware of the standard and to follow it. Still, he says it doesn’t make sense for all projects.

One Sustainable Architect’s Viewpoint

One of the other respondents who had an unusual and dissenting viewpoint was Dan Johnson of Arkin Tilt Architects in Berkeley. They’re just finishing a LEED Platinum house in Palo Alto. Although most of their projects are not certified in any rating system, they are nonetheless quite advanced: off grid, energy independent, passive solar design, renewable energy systems, water collection, extensive attention to sustainable material selection, minimal site impact.

“We prefer to build green without doing paperwork required by a rating system.  Since our future work is based on high performing buildings and client referrals, we already have an incentive to stay at the front of green design without cheating just to make claims. To reduce our clients’ costs, I’d prefer not to spend their money on administrative overhead.  Our name is our green brand.

“I would agree that LEED-H costs the owner lots of money in administrative time, proportionally more for smaller houses. The hours spent on paperwork and calculations do not add any real physical value to the home. The owner could instead spend these thousands of dollars on energy upgrades to the home to get better ecological value for the dollar.

Dan echoed a sentiment that we’ve heard from a few other people, namely, that voluntary certifications don’t do that much to save the planet because the bulk of construction projects will build to code but not beyond. In order to make a real impact of any magnitude, it’s the building codes that have to catch up, and the role of innovation is to prove the concepts, but that’s all it can really do.

“GPR and LEED can validate the work of innovators and help them market their products, but this hasn’t improved the quality of the bulk of new construction [which is mandated by code]. In the absence of high government standards for construction, the LEED award is useful from a consumer’s perspective because it verifies quality claims. However, since LEED-H is no longer very far ahead of the code [in California at least], even the marketing value is not there anymore.

“Now that we have CALGreen, the code minimum has caught up to LEED. It seems that fully of half of the credits in LEED-H are code-minimums now that CALGreen is in effect. So the argument against the usefulness of LEED-H certification has more weight this year. Do owners want to spend money on LEED-H documentation showing that their house meets building code? The cities already provide this service through the plan check and inspection process.

“I would like to see more green compliance handled through the normal code compliance pathway administered by the government, to reduce layers of oversight. It would make sense for LEED-H and GPR to go away, now that the code has caught up, or to raise their standards, to remain relevant as a high bar for innovators. In this regard, PassivHaus and the Living Building Challenge have taken the lead as the high bar for innovators to distinguish themselves. LEED has been so successful in California that LEED is now partially redundant with the building code.

“When a city requires GPR or LEED-H certification as the worst allowable construction, can the architect really take credit for “Leadership…” anymore? In lieu of these award systems, I would like to see HERS launched as a statewide mandatory energy labeling system; new homes are scored on the HERS index during plan check and existing homes are scored at time of sale.

Well, that blew my hair back a little. Both USGBC and BuildItGreen because have been extremely successful because they set a high bar. In California, that bar gets raised up every three years, and very likely these voluntary green standards will continue to improve as well. Sustainability is a moving target, one that every person on Earth will have to wrestle with at some point – on a global, national, local, and personal level – whether we want to or not.

Do’s and Don’ts for LEED for Homes

OK, I’ve recovered sufficiently from the boldness of Dan’s words to abstract a few guidelines for residential architects who may be considering whether to get a California home project “green” certified, either through LEED or through GreenPoint Rating. These notes would still be relevant for other certification programs as well.

• DO review local jurisdictional requirements before doing anything else. Some places require GreenPoint rating based on the sized of the house; others may adopt CALGreen tiers beyond the minimum. Or, they may offer expedited plan checking for certain programs.

• DO ensure that the owner is fully committed to the ideals of sustainability, and not just the label. Why are they doing it?

• DO plan for the chosen certification early, including an ongoing assessment of the impact that the certification may have on project budget and scope of work.

• DON’T forget to factor in any incentive programs that may be available.

• DON’T forget to list the intangible, non-monetary benefits of any sustainable measures. A correctly designed, high-efficiency heating system might cost more, but you’ll be more comfortable. Maybe a lot more comfortable. Ditto using low-VOC materials.

• DO Spend a few hours with a good green building consultant. Spend some time reviewing the required and optional measures in both sets of standards, and make sure that the mandatory measures are feasible and affordable for your project before committing to the whole process. At this point, the owners may feel that they have to choose between scope of work and certification – “If I get LEED certification I won’t be able to afford to do as much as I’d wanted” – so consider carefully how your clients’ money will be spent.

• DO read the manual. Both GreenPoints and LEED for Homes have handbooks describing their requirements in detail. The entire project team should know what the requirements are, and how they will be verified.

• DO try to build up some in-house knowledge of various green building codes and standards: CALGreen, GreenPoints, and LEED. If your’e inclined more towards LEED, get a LEED AP designer on staff if you can. Same goes for BuildItGreen – try to have someone who’s a Certified Green Building Professional, and who knows the GPR system well.

• DO partner with a good green builder – someone who’s worked on LEED or GreenPoint Rated homes before, and who can handle the paperwork.

• DON’T do it just for the label. Jonathan Feldman was emphatic on this point. “Don’t do things just for the points. Do things that you were going to do anyway. You’ll have a better product in the end, better quality control and better durability.”

• DO embrace an integrated design approach. Mitchel Slade, President of Eco-Struction, had some good advice for the entire team, including owner, architect, and builder: “Be malleable. LEED for Homes certification should be one continuous process, not a set of individualized tasks.”

This home in Atherton, CA, built by Eco-Struction, earned LEED Platinum certification.

Epilogue

There’s a lot of room for differing opinion, and no doubt some readers will find some statements above to be objectionable. There simply isn’t room to do full justice to every fact and argument in one blog posting. We encourage you to comment on this article and share your own experiences. All comments are moderated, so please use a valid email address, keep your comments directly relevant to the article, and please be sure that your message is respectfully worded. ;-0

California’s Green Building code went into effect this last January, and recently we had questions from another residential designer about CALGreen – how’s it different from GreenPoint Rating, how does it fit in with Title 24 energy standards, how it works. To answer his questions, I read through the code manual. In addition to the CALGreen code book itself, there’s a very handy cheat sheet that compares CALGreen, GreenPoints, and LEED, for low-rise residential projects. (This version’s probably a little out of date, being from 2010, but you get the idea.) The Q&A below is based partly on that conversation, with special thanks to Doug Hensel of the California Department of Housing and Community Development, who reviewed a draft of this article.

What is the intention of CALGreen?

To reduce environmental impact through better planning, design and construction practices. CALGreen addresses energy, water, material use, and environmental quality (mainly indoor toxicity and comfort).

How is CALGreen structured?

CALGreen is organized into chapters for residential and non-residential buildings. Within each of these, there are mandatory measures that apply  statewide, and voluntary measures, that can be adopted by local building departments.

• Mandatory measures, in Chapters 4 and 5, apply to everyone statewide
• Voluntary measures, located in the Appendices, have two tiers with prerequisite and elective measures
  • Tier 1 Prerequisites are a grouping of measures which set the base for that tier.
  • Tier 2 Prerequisites include all of Tier 1, plus some enhanced or additional measures.
  • Electives are an a la carte collection of additional measures not included elsewhere.

Each tier lists additional prerequisite measures that are mandatory in order to achieve that tier, plus a specified minimum number of electives. Sounds complicated, but it does allow for more flexibility.

California's new Green Building code, which went into effect this past January, has a flexible, multi-tiered approach with both mandatory and elective measures.

What is the rationale behind CALGreen’s tiered requirements?

Voluntary tiers are just that: voluntary. Local authorities can adopt these tiers, thus making them mandatory – in that location only. There’s a note that local building officials can grant exemptions to these tiers in individual cases, in the case of “practical difficulties”. The tier concept was developed in order to allow some of the more progressive jurisdictions to go beyond the code minimum, while still maintaining a level of consistency throughout the state.

What parties, interests, or types of experts were involved in CALGreen’s creation and formulation?

Participants and stakeholders include various California state agencies, as well as model code organizations, building officials, and representatives from the construction industry, the environmental community, the green building industry, and the design community.  BuildItGreen, the private consortium that came up with the GreenPoint Rated system, is not named as a contributor to CALGreen in the official code book, but it can’t be coincidence that many measures are almost identical between GreenPoints and CALGreen.

Who owns CALGreen?

CALGreen is published by the Building Standards Commission, although they don’t determine all of the content by themselves. For residential projects, the CA Department of Housing and Community Development has the primary role in developing the regulations. Various other agencies are charged with determining CALGreen requirements based on the type of occupancy. The Building Standards Commission has the primary role in developing the green building regulations for non-residential projects with the exception of certain types of buildings such as public schools and hospitals.

How does CALGreen fit into other code requirements?

CALGreen goes along with all the other California building codes and standards: Building, Electrical, Mechanical, Plumbing, Fire, and Energy. Apparently CALGreen trumps them in places where they might differ. In general “the most restrictive requirements shall prevail.” Similar to these other codes, local agencies have a lot of freedom to make specific amendments to the CALGreen code – those amendments apply only within that jurisdiction.

Is CALGreen now mandatory everywhere in CA? Are there guidelines for its applicability to different types of projects (eg remodels vs new construction, etc)?

Yes, it’s now the law. Applicability is by major type of construction, for example low-rise residential vs hospital. Both the HCD and the BSC have guidelines on their web sites providing further assistance.

Are there special certified CALGreen consultants who help homeowners and designers plan ahead on their design projects? What is their methodology?

The International Code Council (ICC) offers certification exams for CALGreen. There’s also a group called CALGreen Training which appears to be a private organization. I don’t think the latter training results in “certified” anything (which would involve a test), but there’s a Certificate of Completion. Training can be delivered online, through webinars, or in person. Their page of Helpful Info is quite informative.

How will CALGreen be enforced? I see things like “Construction Materials Protected From Moisture Damage” which means frequent site inspections during construction. Who is in charge of enforcing it, and at what points in the project?

Local building officials and inspectors.

How does Title 24 energy compliance fit into CALGreen?

California’s “green building” code goes beyond energy performance to encompass all sorts of things like reduced construction waste, water conservation, non-toxic sealants, renewable materials, etc. By contrast the California energy standard (also known as Title 24, Part 6) is primarily on promoting more energy-efficient buildings, and only considers the fixed infrastructure: building envelope, heating and cooling, water heating, some lighting restrictions. So it’s more limited in scope than “green building” or “sustainability”. It’s one thing for a design client to say “I want it to be green” and quite another for them to decide HOW that will be accomplished. Creating energy-efficient buildings is part of green building, but green building encompasses a lot more than direct energy usage.

One thing to note about CALGreen is that the upper tiers insist on exceeding Title 24 by either 15% or 30%. That can be a huge “gotcha” if your house has a lot of glass.

These levels coincide with other energy incentives that are currently available. In any case, don’t wait until the day before submittal to run your Title 24 report. In order to beat Title 24 at all, you have to use the energy modeling method – which asks for specifics about things like mechanical systems, windows, and insulation. Beating Title 24 is getting harder and harder, often requiring additional tests and material substitutions. It’s not last-minute stuff.

Why does CALGreen want 15% over Title 24? Isn’t Title 24 already the code? How can a code require exceeding the code?

You will need a MENSA level IQ to understand the reasoning, but it looks like the California Energy Commission and the Department of Housing and Community Development are quibbling over the meaning of “green building”. So, CALGreen says meet Title 24, but the CEC (which develops the California energy code) thinks that the term “green building” should only apply to buildings that exceed Title 24 by 15% or more.

When people ask me how a building code can exceed itself, I feel like I need a MENSA-level IQ. Suffice it to say that different parts of the same overall building code can differ.

Another example of “code that exceeds the code” is water use. CALGreen has a mandatory measure saying that residential water use has to be 20% below the maximum allowable by the California Building Standards Code. It’s enough to drive one mad. The good news is that there will more work for code consultants, potentially reducing unemployment.

How do the following agencies (BSC, HCD, and CEC) interact in terms of exerting authority? Is one a subsidiary of the other or are they independent agencies?

State agencies are given various authorities by the California legislature. Similar to laws of Congress – once that law is passed, it’s out of the hands of the lawmakers, the mandate goes into the hands of the state agencies to interpret, then implement, this mandate. Then, local government enforces it. For CALGreen, local officials review the code to make determinations for each specific project and circumstance. Energy efficiency is a subsidiary or detail portion under overall CALGreen, but neither the Department of Housing and Community Development nor the Building Standards Commission has the authority to set mandatory energy policy in California. The CALGreen code doesn’t spell out the energy standards in detail; that is deferred to the California Energy Center. However, the BSC must approve all energy regulations adopted by the CEC prior to publication.

Do the residential requirements apply to remodels?

No. CALGreen only applies to newly constructed buildings. The definition of “newly constructed” does not include additions, alterations, or repairs.

How was it determined which items ended up in the CALGreen code and which were omitted?

The overall approach is to make it incremental, but state the long-term goals as well. This gives people a chance to learn the new ways and adapt, but they can see farther ahead and go beyond the requirements if they want.

Yesterday's futurism leads to today's advances. The bathysphere on the left was used in 1930 to descend around 3,000 feet - the deepest at that time. Now, deep sea scientists are entering even more extreme environments, allowing creatures like this deep sea isopod on the right and even deep-sea vents at the bottom of the ocean to be observed and captured on film.

Today’s futuristic dream is tomorrow’s baseline. For example, the CEC has a goal of all new homes being Net Zero by 2030. If you tried to enforce that one today, no one would be ready – costs would be prohibitive, and there would be a shortage of qualified designers and builders with the know-how to make it work. But, by incrementally tightening energy requirements, it gives time for new solutions and methods to be developed and tested.

Are there requirements for habitat conservation?

One area that seems to be omitted from CALGreen, and largely from GreenPoints as well, is overall habitat conservation where the natural state of the site is left pristine and undisturbed, as in a nature preserve. This would fall under construction (to build carefully and not destroy any more habitat than was necessary) and also under site planning. The closest both these systems come is a topsoil conservation feature, and some items about low-water landscaping with native species. GreenPoints does have points for unspecified “innovations”.

CALGreen says that it doesn’t want to restrict innovation, but there are no specifics. I think they’re deferring detailed habitat rules to local jurisdictions. CALGreen does have a completely voluntary site selection guideline encouraging the re-use of previously developed sites, which would promote the same goals.

What is the difference between CALGreen and GreenPoints?

CALGreen is a mandatory code, and it’s statewide law, with mandatory measures and additional prerequisites by tier. GreenPoints is 100% voluntary, unless a local jurisdiction decides to require it. The concept of “GreenPoint Rated” doesn’t exist in CALGreen. There’s no such thing as “CALGreen Rated”. Either you meet the requirements set forth in CALGreen at the level set by your local authority, or you don’t.

GreenPoint Rating encourages a project to achieve the highest score possible through the inclusion of a mostly voluntary list of electives. There are a few “required” items, but most of it’s discretionary. A local jurisdiction can require all projects to be GreenPoint Rated, and to meet a minimum score, but they usually don’t say beyond that which electives you must use. This allows a lot of flexibility.

The idea of GreenPoint Rating is that there’s some level of follow-up during construction by a certified independent GreenPoint Rater to verify that the measures are being followed correctly. In fact, you can’t complete the rating process until the house is completed. This makes the score more credible. CALGreen requirements, like other code requirements, are enforced by local building authorities at various points in the project: permit submittal, various inspections during construction for things like foundation, electrical, and final inspection.

Both GreenPoint Rating and CALGreen could be used during initial planning stages as an idea generator for someone who wanted a “green” project but didn’t know how to go about it. It seems that GreenPoints would be a little better for this – it goes more beyond the minimum, and is more specific in some areas, particularly landscaping. Working directly with a GreenPoint Rater as a consultant during initial planning stages can help identify which GreenPoint features are most acceptable, desirable, and feasible.

The GreenPoint Rated system is a bit more specific about water conservation measures available for landscaping. It's not only water use, but whether plants are "native" that counts.

We haven’t mentioned LEED that much, but the LEED certification process also involves a special LEED certified consultant. It’s been criticized as being too expensive and cumbersome for single family residential projects. GreenPoints does add some cost for the consultant, but it’s a lot more reasonable.

Why do we need CALGreen if we already have GreenPoints, or vice versa?

Good question, especially if you’re building in a town that requires both GreenPoint Rating and some of the CALGreen voluntary tiers. I would guess that GreenPoint Rating was a bit quicker to develop, not being so encumbered by bureaucratic process, and it served as a warm-up to incent people to move ahead. GreenPoints is a good road map – the measures are simpler to understand, and clearly written.

Doug Hensel of the HCD rephrased this a bit more diplomatically, “CALGreen is mandatory in all cities and counties, and will thus capture many more buildings than GreenPoints alone. Contrary to GreenPoints, CALGreen is developed using protocols set forth in the Building Standards Law, which require an open and transparent process of public vetting and participation.”

How can a designer or homeowner reduce confusion if their project requires both CALGreen and GreenPoint Rating?

Best thing would be to work with a consultant who’s got dual credentials in both CALGreen training and as a GreenPoint Rater, and involve this person early in the project. They’re not the project manager, though. That would probably be either the owner, the designer (if used), or the builder.

Selecting a good builder is important – and not just going with the lowest cost bidder, either. Get someone who’s already bothered to get a Green Builder certification without being forced into it. If the project involves a licensed architect, the architect should also be familiar enough with local codes to stay within them. It helps if the major parties are already experienced with local issues, including working with the local building department.

How does the energy standard set forth in Title 24 fit into GreenPoint Rating?

GreenPoint Rating also has a mandatory requirement of exceeding Title 24 by 15% or more. Local authorities seem to have two levels of GreenPoint adoption. The first level requires a GreenPoint Checklist at submittal time, showing which features are included in the design. It’s for informational purposes only. The second level requires full GreenPoint Rating, and sometimes a minimum GreenPoint score. This is harder to do, and involves a lot of verifications – including beating Title 24 by 15%.

Again, plan ahead – check with the local building department that has authority over the project, and find out what all their green requirements are. Are they requiring any CALGreen tiers above the mandatory minimums? Are they using the GreenPoint Checklist? Do they require each project to be fully GreenPoint Rated? Do these requirements apply differently based on the project itself, i.e, its size? What other green building requirements do they have? There is no escape from reading the fine print, but we hope that it’ll make a bit more sense now, after reading this article.

Epilogue

I’d sent a draft of this article to Doug Hensel at the Department of Housing and Community Development for comment, not really expecting any response, but he called me right away and sent me a commented version. I incorporated most of his comments (but kept the comment about bureaucracy). He also pointed me to the page containing ALL the CALGreen documents: the CALGreen code itself, a user-friendly guide to CALGreen for low-rise residential buildings, and a slew of CALGreen compliance forms and worksheets for everything from construction waste management to finish flooring materials.

Remember last week, when we were talking about glass houses? Well, here’s another Title 24 case study on a 4,500 SF house, also from Swatt|Miers Architects. This house had almost 60% glazing to floor area, much of it custom built on site: 564 square feet of single paned butt glazed corner windows, 540 square feet of frameless glazing, a steel framed window, a 30 foot tall translucent window in a stair tower, 300 square feet of skylights, and a custom built wood screen interspersed with glass panels. That’s almost 2,700 square feet of glass.

And, to make the challenge that much more… piquant… it was in California climate zone 2 (Sonoma – HOT)… AND, they needed to beat California’s Title 24 energy standard by 15% because of local ordinances. It was the combination of all that single glazed area with the climate zone that concerned us the most. But, we had a reputation to maintain, and our motto to designers was, “We’ll never tell you that you have to shrink your windows.”

(Above image courtesy Swatt|Miers Architects.)

Well, we did end up telling them that they would have to find a way to make the butt glazing work with double panes (which we described in our article on window performance). So I suppose now we have broken our cardinal rule of never impacting the visible design.

Complex Shapes

Although the design was entirely based on rectangular planes, the volumes didn’t always line up one stacked directly over the other. This meant that there were some extra floor and roof areas to account for, and there were some subtle variations in building height, too. Most of the time, this can be generalized, but in this case we wanted to be as exact with every surface area as we could, so that we could claim the maximum thermal mass credit. I knew the planners might be reviewing the report against the drawings with a fine-toothed comb, and we needed to be prepared to respond to any comments with a solid grasp of facts.

Wood framed overhanging floor areas were modeled separately from the slab flooring on the main level.

Start at the Beginning, Grasshopper

As we mentioned in the previous case study, we try to start at a basic level with whatever systems information we have from the designer, and then work up from there. The main heating system was radiant, with A/C. On the plus side, the design called for slab flooring, with gypcrete on the upper level – this thermal mass gave us a ray of hope. Even so, the first trial was dismal. 73% below the standard. Heating was missing by 75% and cooling was missing by a whopping -136%. Only pride kept me from throwing in the towel – pride and curiosity.

“Patience, Grasshopper,” I said to myself. “Just do what you usually do, and don’t say anything until you have some good news to report.” So, here’s what we did, and what worked the best.

Cool Roof/Radiant Barrier. Although this seems like a minor place to start, we’d have to try a cool roof at some point, and it might actually help in Sonoma. The cool roof did make a difference (down to -67%), although the cooling improvements were offset by a small detriment on the heating side. What we really needed was a selectively cool roof, that changes color based on outside temperature – maybe someday soon there will be such a thing. The radiant barrier helped less, and they would have had to change the roof construction to include it. The gains from the barrier didn’t justify including it – unless we absolutely had to.

Wall insulation. Next, we upped the wall insulation from the requisite R13 to R21. That pushed us from -67% to -55%. Pretty good, but still way behind. The designer had thoughtfully provided us with the wall assemblies, so we knew that the cavities were 2 x 6 – large enough to fit R21.

The designer provided us with complete details, which helped us to ascertain how much insulation we could specify in the energy model. Image courtesy Swatt|Miers Architects.

Ducts. There would be both heating and cooling ducts in this project. Although the main heating system was radiant, there would be a forced air backup. We couldn’t model both systems, but we had to keep the heating ducts in the energy model, which cost us. We did verify with the designer that the ducts would be located within conditioned space, which gave a credit. And, we added the HERS test for duct leakage, which brought us from -55% to -40%. (Actually, we tried eliminating the heating ducts and it didn’t help as much as it had on other projects.)

Blower Door Test. With heating and cooling ducts within conditioned space and the duct test taking us to -40%, we added another HERS test – the blower door test, which measures the airtightness of the entire home. Doing these HERS tests on a sizeable house such as this was bound to be challenging, so we stressed to the designer that they, and their builder, should read our article on HERS tests so that they knew what was involved. The builder in particular would need to know that the project was required to pass these tests. The blower door took us from -40% to -37%, not that much. Well, we’d keep it in for now, since it was looking like we’d need every last inch of compliance.

A/C Verifications. Next, we tried adding the HERS tests that apply to air conditioning systems: test for refrigerant charge, airflow, fan watt draw. These took us from -37% to -32%. I had hoped for more. We tried upping the A/C SEER from the standard 13 up to 18 SEER, which, together with the HERS tests, brought us to -29.5%. One thing to note is that often, the HERS tests have more of an impact on compliance than simply upping the SEER. But, all of this was simply postponing the day of reckoning, which was to attack the windows.

Window Performance

As with the other Swatt|Miers case study, we divided up all the window areas by type: Butt glazed corners, frameless wall insets, the stair tower, the custom steel window, various sliding pocket doors, operable casements, the 40 foot long wood screen window on the upper gallery, and the skylights. The design called for various overhangs, including a large canopy extending over the main house and a separate guest house. Most of the window framing was metal, which is not as good an insulator as wood.

Initially, I used the performance specs from Efficient Windows as a starting point for estimating all the custom areas, assuming that all windows with the exception of the corner butt glazing would be double paned, low e glass. There was a lot of back and forth with the designer to establish the composition and construction of the various custom windows. We couldn’t go any better than the standard on most of these (we were lucky to get the standard). The casements and the sliding pocket doors were Fleetwood window products, with numbers that we could look up.

I asked around and searched for information on whether any sort of single glazed window could ever be “high performing”. Alas, there was no magic glass. The experts all informed me that the main factor in window performance is 1) multiple panes with insulating layers of air or gas fill 2) airtightness of the frame itself and 3) insulating properties of the framing material. There was no such thing as a thermally  broken, metal framed window with single glazing, because why? There wouldn’t be any demand for it.

But we were still at -29%. Something had to give. So, I broke our rule and made all those butt glazed corner windows double glazed. That took us to -11%. And then, I modeled the Fleetwood windows using the best numbers they had available for each type. That took us to -6%. At the same time, I put out the word to see if anyone had successfully built a corner glazed window with double paned glass, because I knew that the designer really wanted to keep that transparent appearance, and putting a spacer bar on the corners would be a major disappointment, to say the least.

And it still wasn’t enough. Even adding the dreaded QII test (a HERS test where every bit of insulation is inspected as it’s installed during construction) wasn’t enough, although the QII did bring us from -11% to -0.8%. So close – and yet not close enough, considering that we had another 15% to go.

Interior Mass Surfaces

At this point I dragged Mark English over and made him review the entire drawing set plus all the details. As an experienced architect who’s been designing and building homes for 25 years, I figured he’d see a few things that I had missed, and he would make sure we didn’t take too many liberties with the wall and roof cavities.

Based on consultations with Mark and numerous exchanges with the designer to verify the exact location of every wall and floor finish, we added the thermal mass of a dramatic 2-story stone veneer wall, over 1475 SF of thermal mass. Additionally we included all the tile flooring in the bathrooms, countertops, and the gypcrete from the second floor’s suspended slab floor. Even though this floor was largely covered by wood or carpet, it still yielded some credit. That took us from -0.8% to +12%.

Upon our request, the designer provided us with the location of vertical thermal mass surfaces - stone veneer walls - which we could then include in the energy model. Image courtesy Swatt|Miers Architects.

And it still wasn’t quite enough. I felt like a magician reaching into a hat for another rabbit and coming up with a hamster instead.

What the Designer Said

I figured it was time to fill in the designer with our progress to date, and test the waters about making the butt glazed windows double paned. It might be a good time to insist on an uber-efficient water heater. We’d actually started with a reasonably efficient one, a .80 energy factor, but without further information, I was hesitant to commit to anything extreme. Eventually we would have to include the actual models they were using, and there would likely be more than one with a house that size anyway. I don’t think they had worked out the mechanical systems to that detail, so now was a great time to test and suggest a few things.

But before we reached into our top hat for that last rabbit (the water heater itself), we tried a few more things just to see what would happen.

Solar water heating credit. The design hadn’t specified solar equipment of any kind. Well so what? Maybe it would let them keep that single glazing, although I doubted that.  Even though there’s no credit for the use of renewable energy for electricity or heat, there is Title 24 credit for solar hot water. It’s based on the percentage of hot water that the home is expected to get from solar, and sure enough, set this percentage high enough and the compliance score improved.  So, by pushing this number to an unrealistically high 50% we were able to inch our compliance from +12% over to 17% over, although I doubted that this would actually work.

And why not? Well, the problem with it is that you still need some kind of indirect storage tank to ensure hot water in the evening, unless you only plan to shower at high noon. In addition, this home would have extra water heating demand because of the radiant heating. But hey… we reached our goal, in theory at least.

Higher Solar Heat Gain on Some Windows

On the last case study, I had, purely out of curiosity, tested a series of window performance combinations just to see what would happen. Although a low U value window was always the best choice, because it provided thermal insulation for both hot and cold temperatures, what could we do if the best U value we could find was average – if that? Since we had so many custom windows that would be built in the field, we couldn’t make aggressive assumptions about them.

So, I inched up just the solar heat gain on the Fleetwood windows, while keeping the U value the same. This would allow at least some glazing areas to keep up their insulating value, while allowing a little more solar heat. Although originally the design had lagged more on cooling, it was now the heating side that had all the shortfall. We were actually ahead on cooling. This latest change brought us from 17% over to 18% over, so it didn’t make a huge difference. Heating was better, cooling lost a bit.

Skylights

The skylights were another big unknown. There were a lot of them, and the designer indicated they didn’t want wood framed because they were concerned about leaks and such. Then they selected a manufacturer who actually had pretty good numbers, which brought us from +18% to +21% over.

Highest Efficiency Boiler

It was time to pull out our very last rabbit, which was to boost the water heater performance as far as it would go. By specifying a boiler with a 95% efficiency, and keeping a solar hot water credit at 25% (still probably too aggressive), we got the house to exceed Title 24 by 32%. At this point, we dialed back the Fleetwood windows to the actual numbers (Westwood and Norwood product lines, dual glazed low E, thermally broken, but no argon – air fill), and removed the solar hot water credit altogether. We kept the HERS testing for credits: the three A/C tests and the duct test.

The final score? It came out as exceeding Title 24 by 25%. This would give them a little margin if by some chance it didn’t pass every HERS test. Some of those tests were worth GreenPoints, too. So, chances are this house will earn a respectable GreenPoint Rated score as well once construction is complete.

A few final notes follow, on what the designer did to help us, and a note on modeling multiple zones.

Detailed Wall and Floor Assemblies

This was one of the few projects where the designer provided us with detailed wall and floor assemblies, 3 drawing sheets of it. This was great, because we could see exactly where the gypcrete was, which portions of the floor were covered (and with what) and which walls had interior stone veneers.

Although we don't always have to model every layer in the floor, in some cases it helps to know exactly what's in there. Image courtesy Swatt|Miers Architects.

Modeling Multiple Heating and Cooling Zones

This was something that we would have resorted to only at gunpoint, because it’s very time-consuming. Essentially, you model each zone as a separate volume – including floors, walls, and ceilings – as if it were its own little house. Title 24 gives credit for this, but I’ve only ever done it once on a private home, and we had no way of knowing how much it would help unless we tried it.

Actually the real question is whether an all-glass pavilion can still comply with the new version of California’s Title 24 energy code. Although Title 24 has been around since the 1970s, it is only now that designers are feeling the pinch. Given the increasing strictness of the energy code, what can an architect do if he (or she) wants to create designs with dramatic glass curtain walls?

The “glass house” shown on the cover image is, of course, Philip Johnson’s famous Modernist masterpiece, also called the Glass House. Even that house could, with the right high-performing window system, comply with Title 24 requirements – I tested it out. But, let’s talk about some more current designs for our case study.

When we got our first Title 24 project from Swatt|Miers Architects, I didn’t really know if we’d be able to finesse it. We had never had a project quite like it before. But then I remember seeing an award-winning Net Zero home in Truro, Massachusetts (by Zero Energy Design) which had acres of glass everywhere. If they could make it work in a cold place like Massachusetts, surely we could do the same in California!

This Net Zero home in Truro, Massachusetts, was designed by Zero Energy Design. And yet, this house still manages to be efficient even with all this glass. Photos: Eric Roth.

Our first Title 24 project from Swatt|Miers Architects was a 6,000 SF all-glass pavilion with a generous roof,  a custom window wall on one side, and heated slab floors. On the plus side, the roof included large shading overhangs, and we had ample time and flexibility to select high-efficiency heating and water heating systems. There were no large skylights or ductwork to worry about, either. The house was located in a moderate climate zone, so they weren’t even going to install any cooling systems at all.

Another big plus was they didn’t have any “beyond compliance” goals such as GreenPoints. So, we didn’t have to beat the standard by 15% or more. As you’ll see in a minute, that would have been possible, but very expensive.

On the challenge side, there was almost 5,000 square feet of glazing – 75% of the conditioned floor area. In addition, the design called for metal framed windows, which are inherently less efficient than windows framed in wood or vinyl. Even thermally broken metal windows can’t always match the performance of wood.

This house had 75% glazing to floor area and yet, it still managed to comply with California's Title 24 energy requirements. Design Courtesy Swatt|Miers Architects.

Strategy: Start Low, Increment Up

We usually start by running each project with baseline assumptions, usually the same ones used for the prescriptive Title 24 method. The Title 24 prescriptive method sets forth minimum requirements for things like heating and cooling performance, insulation levels, maximum allowable glazing areas, and window performance – but it’s all or nothing. Either you meet every requirement, or you have to use the performance modeling method to satisfy Title 24. The software model has some built-in generic inputs for things like water heaters that also assumes a very basic level of compliance.

Using the software modeling method of Title 24 energy compliance, a house can fall below the standard in one area as long as it makes up for that shortfall in another area.

In this case, the first trial missed by -76%, with shortfalls on heating and water heating. Surprisingly, cooling was not a problem – at least, not in the model. Still -76% seems like a big, scary number – one which we attacked incrementally.

Preliminary Trials with Insulation and Water Heating

Increasing insulation levels from R13 to R21 brought it to -67%. There wasn’t that much wall to work with, the walls being mostly glass, which is measured by window performance rather than insulation. The roof already had plenty of insulation, and adding more past a certain point had a negligible impact.

Just as a test, adding an overhang over the South window wall (which didn’t have one) actually made it worse! That’s one thing about trade-offs. Sometimes a measure that helps with cooling will create more load on the heating side, and heating was what we needed to fix. But this design didn’t specify an overhang there, and even when there are overhangs, modeling them is optional.

Next, we tried upping the water heater performance. Originally we’d specified a generic setting, because the mech hadn’t been worked out yet. For a house this size, over 6,000 SF, you probably wouldn’t have a single heater anyway, and you definitely wouldn’t be running all the hot water AND the radiant through one heater. So we had started with a 75 gallon storage tank with a .75 energy factor – legacy numbers.

A tankless heater with a storage tank, with 2 separate systems, and a higher energy factor, got us down to only -49% below Title 24 requirements.

Main Trials: Windows

But all this was simply prep, because the windows were going to be the biggest challenge. The window performance factors that are important for Title 24 are the U value, which measures thermal performance (keeps winter heat in), and the Solar Heat Gain Coefficient (keeps summer sun’s heat out). We had all been thinking that with all that glass, cooling would be the concern, and we’d have to get the lowest SHGC we could find. Not so. It was the U factor on all those windows that would make or break our compliance.

In fact, having a higher SHGC might help because we could afford to lose some cooling margin if the solar heat gain would actually help on the heating side. Passive solar designs in far North latitudes try to leverage the sun’s heat, especially in the wintertime when there’s so much less of it. We don’t normally think that way in California, but occasionally a higher SHGC can actually help, especially on the East wall. The reasoning is that solar energy on the east, when the sun is just rising, can help the house to recover from cooler nighttime temperatures.

Typical test results from Fleetwood Windows, available online, show just how many options there can be even within one product line.

The Title 24 prescriptive minimum for window performance is .40 U/.35 SHGC, lower being better for both these numbers. That’s pretty tough, considering that most ordinary metal framed windows run around .50 or .60 U factor, even for double glazed, “Low E” glass. We had started with the generic “metal double glazed low e” input which is around .65/.40. This project specified Fleetwood windows, which has several product lines with a wide array of options for glazing, thermal breaks, gas fills, and even glass types. All of their test results are easy to find, too.

We also modeled each window opening separately (over 77 of them), so that we could use different performance numbers for each window type: there were Casements, Awnings, Fixed, Sliding, and a couple of custom settings. That way if a better performance could be had from the fixed windows but not from the operable ones, we could include it. Sometimes clients have also asked us to use different settings for different cardinal directions, for example, using a more expensive but spectrally selective glass on a western or southern wall where it might matter the most.

For the Swatt|Miers design, Green Compliance Plus modeled over 70 different glazing areas in order to account for small performance variations among window types.

U Factor or SHGC – Which Is More Important?

Although we were more concerned with the U factor, it was possible that testing different combinations of U and SHGC factors might yield some interesting information. So, we spent a lot of time trying very low U/low SHGC combinations. We also tried some average U with very high SHGC windows, as well as trials where we kept one number the same and varying the other one up and down to see what would happen.

A low U factor was the best choice, regardless of SHGC – but, this might not be achievable, even if they used the more expensive, thermally broken frames. Of course, triple glazing with argon gas fill would help a lot, too – I’m not sure what the quote was for 4,500 square feet of windows with triple glazing/argon/thermal breaks, but it would have killed the project budget. We had to find some way to make it work with double glazing.

A U value of .35 or under would be better overall. A U value of .25 would be awesome. If the U value was low enough, like .30, it didn’t matter as much what the SHGC was. In fact, with a U value of .25 some of the runs came out almost 40% over compliance! Some interesting window results: With a higher U value, a moderate solar heat gain acted to compensate somewhat for heating loss. It was almost as if there existed a second, smaller “peak” of outliers which, if I had a lot more time, I’d try to graph in more detail.

Of course, it’s all very well to say that we need a window with a U value under .30. The U value was the one thing that most limited us, because with the window products and framing materials selected, it simply wasn’t possible or cost-effective to get down that low. And, specifying an artificially high SHGC just to “make the numbers” didn’t make sense. But then again, neither did specifying triple glazed, argon filled windows in a mild California climate zone.

Custom Window Wall

The custom window wall on the South wall was another challenge. Fortunately, this area was wood framed – not aluminum like the rest of the windows. The wood framing would help with thermal performance, and the plans already called for double glazing with Low E glass. However, since there were no formal NFRC test results for it, what numbers could we safely assume for performance? As it turns out, we checked with the local Planning department for the project’s location, and they indicated that using the Title 24 prescriptive standard, .40 U/.35 SHGC, would be acceptable. This standard already assumes a wood framed, double glazed, low E glass window – so it made sense to use it for the custom window areas.

We might not be so lucky in another jurisdiction, though. The plan checkers have some leeway to use their own judgment and, if we’d been in another area, we could have been asked a lot more questions about materials, glass types, etc. – and possibly we might have had to use less forgiving numbers.

Additional Measures

In the actual project, we tried a few more things. One was a super-efficient water heater. Most water heaters are in the .65-.80 range for energy efficiency, but there are some out there that go almost to .95, so by creatively assuming that they would use the best systems available, we could at least present that as an option for compliance.

We called out each area of interior exposed thermal mass – exposed stone, tile, and concrete – because usually this helps with Title 24 calculations.

And, as a last resort, we could have called for some HERS verifications for extra compliance credit. Our article on HERS testing describes each of these tests in detail: duct blaster, blower door, QII, and various tests on the A/C system. Of course, not all these tests were available on this project. With radiant heating and no A/C, there were no ducts to test. And, the various A/C tests – refrigerant charge, fan watt draw, airflow, and verified EER – couldn’t be used, either.

Would Cooling Be an Issue in the Real World?

Initially we were surprised that cooling was not a problem, and we were all wondering how realistic that would be once the house was actually built and inhabited. Title 24 intentionally ignores some real-world conditions such as landforms and shade trees, but it does apply location-specific climate data on top of the broader “climate zone” designation. The designer expressed concern that with a high SHGC window, the house would be too warm during the summer, especially along the South side. And really, to us it didn’t make sense to use an artificially obtained number when the most straightforward thing to do would be to use California standard Low-E, low SHGC glazing.

Would Philip Johnson’s Glass House Meet Title 24 Energy Requirements?

Just for fun, I did a quick test of Philip Johnson’s Glass House, using floor plans and dimensions that I was able to find on Google… no guarantees on accuracy, but it seemed like it was worth a try. The trials included three California climate zones: Woodside (Zone 3), Tahoe (Zone 16) and Livermore (Zone 2) and a few compass orientations for 0, 45, and 90. For starters, I assumed double glazing and Low E glass, with the same numbers as a wood frame would be. And, for heating I assumed radiant heated slab flooring… which I think is the actual method.

Title 24 ignores shade trees, which in the case of Philip Johnson's Glass House are a major environmental feature.

The compass orientation didn’t matter that much – it mattered a little – but, the location had a bigger effect, mainly in the balance between the shortfalls between heating and cooling. No surprise, Livermore had the biggest cooling problem initially.

Setting the glazing to something more like the actual (metal framing, clear glazing) was disastrous for Title 24 compliance. However, when I changed the windows to the “best available” performance numbers – something around .20 U/.20 SHGC – the house complied in all three zones without any further changes.

I've never been inside the actual Glass House. I wonder how comfortable it really is in the winter? There are almost no wintertime images of it.

The Catch – Custom Built Windows Can’t Use NFRC Test Results

In reality, it may not be possible to even obtain pre-manufactured windows of the size that are used in Johnson’s Glass House. And, in order for performance numbers to be valid and acceptable for Title 24, the window units have to be NFRC rated. We’ve discussed this in a previous article, so I can’t assume that the Glass House design as it is now would ever be able to fully comply with Title 24. And, of course, the Title 24 modeling software only has climate data for California, not Connecticut where the house is actually located. Nonetheless, it could comply a lot more easily than some other projects we’ve worked on.

Another Glass House: Olson Kundig’s Glass Farmhouse

As I was looking around for any accounts of the actual comfort of Johnson’s Glass House, I found another, much more recent take on the all-glass house from Olson Kundig Architects, located in Oregon. Alas, no reports on actual energy use or comfort here, either – but Kundig did employ solar design features and high-performing glass and took some care to adapt the house to the local climate. You can see some nice images and a description at The Contemporist.