Up until recently, residential architects varied in their knowledge of heating and cooling systems. Many architects whose focus is primarily one-off, custom residential projects, have simply assumed some form of conditioning and then left the details to their contractor. Finalizing the details may not occur until late in the project, long after the opportunity for building optimization has passed.

What most people also don’t realize is that the manner in which a system is installed and configured can have a dramatic effect on how much it can deliver. Most private residential projects haven’t budgeted for a separate mechanical engineer upfront to optimize efficiencies among systems or to suggest additional measures during the design phase.

Beyond that, of course, there’s another reason for California architects to start paying closer attention to systems upfront: Title 24 energy compliance. The new energy code is stricter, and the default assumptions are no longer good enough for some homes to pass. The Title 24 is typically done when submitting to Planning, at the end of Schematic Design – long before anyone thinks about the furnace other than to say, “Oh yeah, we were going to keep the existing furnace and ductwork from 1956.”

A typical forced-air heating system showing heating unit in basement, supply and return ducts throughouth the home, with recirculation fan in attic.

What happens to your Title 24 when you don’t plan ahead?

If you don’t plan ahead, you could learn of expensive additional measures only on the day of the planned submittal, and end up making important trade-off decisions in haste. We are seeing cases where our clients (other architects) had carefully scoped the project budget and they depend upon being able to reuse existing elements such as windows. However, if the project requires the performance method of Title 24 compliance, and we have to model the whole house, those existing windows can make compliance all but impossible to achieve.

Same thing with systems. Once a house is already teetering on the brink of not passing, we need to look for measures to improve performance, and something’s gotta give. You could end up having to insulate more than you’d planned, or replacing a furnace with a more efficient model, or replacing more windows than you anticipated. Yes, we could tell you to shrink the glazing (gasp!) but this would compromise the design intent, which we try to avoid.

Optimizing building efficiency can involve many inter-dependent factors.

Typically we don’t even get information on existing windows or walls, and we have to assume the worst. We’ve also had to work hard to convince people that window efficiency really does make a huge difference, especially now. And, even if we agree on performance numbers that are workable, the project is very sensitive to last-minute changes in the field. We’ve had to add HERS verifications in a number of instances for additional “compliance credits”.

What needs to be known about systems upfront for Title 24 compliance?

First, it’s essential to know the basic system type and configuration. Is it a gas furnace or hydronic heat? A split system with A/C and a heat pump? Is it a tankless water heater or standard 50 gallon storage, or tankless with indirect storage tank? If you have radiant heating, is there a separate water heater for that? How many heating zones are there?

One reason is that some of the above-mentioned compliance credits aren’t available for all system types – you can’t use the HERS duct testing credit on a ductless hydronic system, for example, and you can’t verify refrigerant levels in the A/C system if there’s no cooling installed. Discovering something like this during construction might be one reason to have to re-do the Title 24 report, and you’d have to make up those lost credits somewhere else in a way that maybe you hadn’t planned or budgeted for.

For Title 24 compliance, consider the basic heating system type and configuration early on. This example shows a 2-story home with radiant heating below, and radiators above, supplied from one boiler which may also supply domestic hot water - although that part is not specified here.

Next, you might have to provisionally select unit manufacturers and models, so that their efficiencies can be used as inputs for the software model. If it turns out you need a higher efficiency model than you’d planned, you at least have time to do some pricing to determine whether it makes more sense to upgrade the system, or perhaps to take other measures elsewhere.

Not all manufacturers post the efficiencies, or sometimes they don’t publish the right ones for Title 24. It can take some time and research to establish what numbers to use, so that these inputs are defensible in the case of an audit. In a nutshell, the main inputs are:

• Gas furnace – AFUE; BTU per hour; default is .80, but you might have to go with .90 or better

• Split or heat pump package system – Heat pump HSPF; default is 7.7; 8 and above are better; goes to 11

• Electric heater – Don’t use this if there’s an alternative. Penalties in Title 24.

• Cooling – SEER; 13 is the minimum; 15-18 is good; however, cooling isn’t as important in this area as it is in SoCal. Many of our Title 24 projects don’t even have A/C.

• Water heater – Energy Factor and for hydronic heating, Recovery Efficiency; tank size; BTU per hour.

• Hydronic – See under water heater.

A house of cards… or what happens to your Title 24 compliance when systems are an afterthought

On projects that are severely constrained in budget and scope, we have had to dig very deep to find measures that are both acceptable to both architect and owner, and which also yield enough performance boost to push the house back into compliance. Usually it’s not just one measure, but a combination of measures all taken together. If any one of those measures is eliminated or altered, then we have to start over – and hope that we can think of something else.

If these measures include HERS tests, then it’s very important that the house is able to pass these tests. This takes coordination with the builder, and assumes quality construction practices. If for some reason these tests can’t be performed, then again we have to make it up elsewhere.

Later in construction it gets even harder to compensate for a change, because measures that might have been possible earlier on are no longer an option. For example, one alteration we worked on was constrained to using single paned clear glazing for “historical reasons”. We had to call out every other measure possible, including replacing the systems, because the one thing that would have made the most sense – better windows – was non-negotiable.

Don't wait until the last possible moment to think about energy compliance. "An ounce of prevention is worth a pound of cure."

A few answers from Jeff King, Bay Area Green Builder

Of course Title 24 is not reality! There are many more factors that influence efficiency and comfort that are NOT recognized within Title 24 (yet) and it’s helpful to know about them because they’re also important to factor into the design early on.  We chatted with Jeff King , a Green Builder whom we’ve interviewed previously, for a reality check on what really works. His experience is mainly in and around San Francisco, working mainly with forced-air and radiant heating systems. His common-sense approach is to use high-efficiency systems and make sure that they’re properly configured and installed.

[Within the interview, my comments are shown in bracketed italic - RF]

How do you size a heating system correctly?

Jeff King: For heating and hot water delivery systems, the systems need to be properly sized – which most are not. Most systems are grossly oversized! This means they don’t operate as efficiently or as comfortably. It’s hard to quantify exactly how many homes have oversized systems, but I would not be surprised at 75%.

To size a system properly means a written evaluation and calculations using Manual J and Manual D, from Air Conditioning Contractors of America. [Manual J now available as software - RF]

Of course most subcontractors rely on a thumbnail view and their own experience of what has worked in the past. For example, the sub might consider the floor area, number of bedrooms and say, “Let’s go with an 80,000 Btu furnace,” when actually, a 40,000 Btu one would be just fine. For replacement systems, subcontractors will just drop in an 80% efficiency system that’s a third to twice as big as what’s really needed, just because that’s what was there before.

In some cases, sizing may be limited by available equipment. For example, you usually can’t buy a gas furnace that’s less than 40,000 Btu, although models with a modulating gas valve can operate in a range from 20,000-60,000 Btu.

How good is the typical installation for forced-air heating systems?

Jeff King: The other important issue is quality of installation. This includes layout and location of various system components. If the layout is an afterthought, it might end up being a lot less efficient, even if the units are top of the line.

Bad Ducts Part 1. Left: Too many ducts. Right: A badly crimped duct.

[One thing that other mechanical experts have stressed is that right-sizing the ductwork for the system that is installed is as important as minimizing bends and duct lengths. If you replace a system but plan to keep the old ductwork, take a close look at what you'll be re-using. - RF]

Jeff King: For forced-air systems, include manual dampers at the plenums for all heating ducts to aid in balancing the system. Sometimes one portion will draw air differently than another. The goal is to have less than a 3 degrees of temperature difference between rooms.

You can get high-performance heating registers, too, but not at Home Depot. The cheaper ones don’t mix air appropriately. You need scooping lovers. A good register should also be directional according to its position in the room. I see bi-directional registers put up against a wall – why? Floor-level registers should mix the air up, while ceiling registers should mix it down.

Ductwork should be sealed with mastic and tested for air leakage. We test all our systems to 5% leakage, because we want to be sure it was done right.

Bad Ducts Part 2. Left: This duct has been strapped to the rafters in a way that cuts off most of the air. Right: Duct sealed with duct tape has a giant leak.

Other aspects of how the system is installed include register locations and duct layouts. You might be able to reuse portions of the old system, but if you start moving walls, then you might have to redo other things as well. This is especially important for contemporary architects, because forced-air heating doesn’t lend itself to ultra-modern open designs. In fact, modern architects often default to radiant heating, because they don’t have to design around bulky ductwork. However, radiant flooring isn’t always a good fit for every client’s need.

Architects don’t need to know it all themselves. What architects need to do, though, is consider system requirements at the Design Development phase, not at the construction phase. If you wait until construction, sometimes the architect has to re-design things like duct chases, because you can’t always re-use all the old stuff.

Bad Ducts Part 3. Here we see un-insulated cooling ducts exposed on the roof in Phoenix, AZ, one of the hottest places in the U.S. All that cooled air going across a hot roof.

Is on-demand water heating always better?

Jeff King: There’s a knee-jerk “green” reaction where people say things like, “I want an on-demand water heater!” Well, if you’ve got a 5,000 SF house with three stories, and bathrooms on either end of the house that don’t adjoin in any way, on-demand water heating is the WORST!

Same thing with radiant flooring. It’s supposed to be more efficient, and sometimes it is – if you want your home to stay at a steady temperature of 68 degrees 24-7-365. But if you like to sleep in a cold house, and some people do, radiant heat is not so great, because it takes too long to heat back up in the morning.

What makes for an effective hot-water installation?

Jeff King: With hot water delivery, it doesn’t matter whether it’s storage or on-demand (tankless). In fact, I won’t install on-demand water heaters unless it’s a hybrid. Hybrids are essentially on-demand but they do have a small storage tank, typically around 2.5 gallons or so. My favorite model is the Eternal Hybrid. You can use it for heating, too, with radiant flooring or hydronic air handlers.

The Eternal Hybrid is 98% efficient. We include a normal recirculating system and pump, but not on a timer. Instead, the pump is motion-activated when someone goes into the shower, with a thermal sensor at the point of use (if the person doesn’t shower immediately, the heater only kicks back on if the pipe goes below a set temperature of say 90 degrees, assuming the water’s at around 110-120)

Certified Green Builder Jeff King's favorite water heater is the Eternal Hybrid.

When we are installing new pipes, we insulate all the hot water pipes all the way to the point of use. Insulated pipes hold the temperature a lot better.

Even better is manually activated water heating. We haven’t talked many clients into this but we did do it on one job where we used motion-activated sensors in the bathrooms, but had a manual activator in the kitchen. It only takes about 30 seconds to heat up the water.

On-demand recirculation pumps are good for tank-style storage too, for water conservation.

How do you account for the heating system during the design phase?

Jeff King: For forced air systems, you need space for the ductwork. Architects should talk to the contractor during design development, and they should consult with a mech engineer early on. Not just a subcontractor, but an engineer. Sometimes you can just thicken a wall or widen a chase, although you might sacrifice some living space.

Other design elements can affect comfort as well, such as large expanses of glass on the north or south walls. Glass on the north can get chilly, while glass on the south of course can cook you in the summer if it’s not shaded. And don’t place the thermostat in direct sun.

The more modern the design is, the more important the systems become, because you can’t leave them as an afterthought. [You don't want unsightly elements intruding into an ultra-minimalist design. - RF]

Another example of duct shame, this one a DIY A/C ducting job. I think the black dots in the photo are actually holes for the cooled air. Not exactly the minimalist modern look.

Louis Kahn designed servant spaces and special half-height floors for mechanical systems in some of his buildings.

Jeff King: That’s an engineer’s way of thinking and it’s great. You need a lot of dough, though!

How do you choose the right system for each project?

Jeff King: Here’s what I do.

1. Ask the client about their lifestyle habits first. Do they want to shut off the heat at night? Or only keep certain rooms warm? Individuals have different comfort needs, too; some people like it cold, while others can’t tolerate it. Depending on which portions of the home are used, when, and by whom, I might use a 2-zone system, or even a split system.
2. Understand how involved the clients want to be with the complexities of their system. Do they want a lot of operational control or a one-button system that’s mostly running in the background?
3. Review the furniture layout. This is important for forced-air systems, because you don’t want a register right next to a 400-year-old antique! And you don’t want heating registers right over someone’s bed. That’s very uncomfortable and unhealthy, too.

Architects can do this, too, and then consult with a mechanical engineer who can help them figure out not only the type of system, but what configuration is most optimal.

[Sometimes we get Title 24 projects where the client decides later on to go with a different type of system - usually changing from forced air gas to radiant. However, changing the system type or configuration later on can require re-calculating the Title 24 - so try to anticipate what systems are being considered and at least do a rough check for the viability of each one for Title 24 compliance.

Will anyone actually notice if you fudge things on the report? Well… first of all, if you're going for any green certifications like GreenPoints or LEED, there's a good chance the energy report itself will get audited. If you are going for the New Solar Homes Partnership, the report will definitely be audited. And, back to our topic of systems here, the system types and efficiencies are shown on the Title 24 report and it's fairly easy for an inspector to spot when a furnace shown as .93 AFUE is actually .80.

Will anyone notice if we specify HERS tests on the Title 24 report but we don't actually perform them? Yes! There is a new process whereby the HERS test results are reported separately and independently, and this documentation must then be provided during final inspection. And once the project's finished there are fewer options for remediation. - RF]

What about radiant flooring installation?

[Jeff King didn't have any specific notes on radiant heating installation, but I did find a good example of how layouts and piping configuration can affect system efficiency and heat distribution. - RF]

The layout of radiant floor piping can affect its performance. The floor on the left will heat unevenly, with a cold spot at one end, while the one on the right should have a more uniform temperature.

What about hydronic forced-air instead of heating the air by gas?

Jeff King: There’s a type of hydronic forced air that uses hot water instead of a gas flame to heat the air. It’s a little lower in heat output, but that can actually be more desirable; the system runs more steadily instead of rapidly cycling on and off. Also it’s less drying than forced air with gas – less intense. Generally with heating systems, you want it to run at a low output continuously.

What you don’t want are peaks and valleys. Blowers and thermostats can mean the temperature rises rapidly and then drops off just as quickly.

The most complex system I ever installed of this type was a Phoenix 120-gallon tank storage water heater with advanced temperature sensors and control. This  unit provided domestic hot water, as well as heating for 2 hydronic air handlers, plus a radiator in one room that we couldn’t put ducts into. Each of these applications needed a different temperature of hot water, though.

• DHW can’t be higher than 120

• Hydronic forced air needs around 135

• The radiator needs 160 degree water.

We had to draw from different parts of the storage tank.

This forced-air and tank system is something I’m doing on my own house right now. I have to live with it myself for a while, gotta walk the walk.

What about ventilation systems?

Jeff King: I haven’t had to do much in the way of ventilation. San Francisco ventilation requirements are minimal. You don’t need A/C here and most ventilation is “just open a window”. A bathroom fan can meet the ventilation requirements. Whole house ventilation makes sense down in the Valley where it’s hot, or for new, airtight homes with cold winters and hot summers.

Isn’t it wasteful to have to rip out elements like existing windows or furnaces that are fairly recent, but not quite recent enough?

Jeff King: Does it really make sense to tear it all out? I’ll quote Kevin Beck, a trainer at BuildItGreen  who says, “I don’t care if the windows are single glazed as long as they seal well against drafts and the walls are insulated. A dual-glazed window here in San Francisco isn’t much better than a really well-sealed regular window.”

Sometimes it doesn’t make sense to tear everything out if it still works well. It’s more about design and getting rid of over-sized pipes or ducts which aren’t needed for more efficient systems. Also remember if the existing ducts may have been poorly installed or sealed, so getting a new unit but connecting it to existing duct pipes might not be enough.

When there’s an opportunity to take an aging system out, then we get the best efficiency we can. The cost is not so much in the equipment as in the labor and installation. The difference between an 80% furnace and a 98% is only about $600 in equipment costs.

What about “alternative” or “cutting edge” or “emerging” system technologies?

Jeff King: I’m not that into the more far-out or experimental technologies. I think more about system longevity. Also I’m wary of them, because what about maintenance? If you install some high-tech invention, there won’t be many people around that even know how to repair it.

The Phoenix water heater I talked about earlier is about the most techno-enabled system we’ve ever installed. Other technologies like ground source heat pumps (geothermal) aren’t great for urban settings because you need land. I haven’t worked with them.

Ross Levy of LSArc<http://www.lsarc-sf.com> designed a system for a Victorian remodel here in San Francisco. The client’s goal is to be NZE and grid independent. [We plan to write a description of this home in a future article. - RF]

Of all the green building guides for homeowners out there, here is one that should be on everyone’s shelf – owners, architects, builders alike. It’s called “Energy Free: Homes for a Small Planet” by Ann V. Edminster, a Bay Area local. Everything I’ve been struggling so hard to explain to our Title 24 clients, even in a limited way, is presented in this book with clarity and accuracy, in a very readable and lively prose style. It’s backed by both the latest research and by personal experience and observation.

The Problem with Mantras

“They want it to be ‘green’…” Neither the client nor the architect had any comprehension or appreciation of “green” other than as a gimmick. The client was an Al Gore fan who had read “An Inconvenient Truth” and suddenly decided mid-design that the new house being designed for him and his girlfriend needed a “zero carbon footprint”. There had previously been vague feel-good conversations about “eco” and “green” but nothing tangible, no specific goals, performance measures, or standards to follow. Unfortunately, neither the client nor the architect understood how much work “zero carbon” actually entailed, and the client hadn’t selected this particular architect for his expertise in green building. He had originally envisioned a luxury home by a “design-oriented” (i.e. Modernist) architect.

"Green zombies" chant the green mantra endlessly, but never stop to think about how to get there.

I can’t tell the whole story here, but it seems that the client was shocked to hear that there might be re-design fees involved, plus a fair amount of additional research. (He and his girlfriend split up in the middle of the project, too – the project was subsequently abandoned.) Perhaps he felt that anyone calling himself an architect should already have the answers. That’s a bit like saying the architect should already have the house designed the moment you set foot in their office.

First, Take A Good Look in the Mirror

But choosing green can be daunting – as if shelling out several hundred thousand dollars or a few million for a custom-built home isn’t daunting enough. If you’re seriously trying to be green, there are so many competing standards and methodologies out there, it can seem overwhelming. And to be honest, there is no shortcut to thinking hard and seriously about it as an owner. You’re not just learning about technology, you’re taking an inventory of yourself, your habits, the real implications of those habits, and what you could do without. It’s also being very honest about what you can’t live without and sticking to your guns about it – even if that need might seem “selfish” rather than “green”. You can’t just engage with an architect, wave your hand like Captain Piccard on Star Trek: The Next Generation, and say “Make it so.”

The hardest work of green design is asking yourself what's really important, and then following through

What we need is a simple guide on HOW to think about building green, meaning how do you go about deciding what your priorities are and then executing them to completion? How do you even define what’s green, or green enough? What kind of science is behind each of the green definitions, anyway? It’s an exercise in complex problem solving – and self-analysis.

Start With Home Energy Consumption

Measuring greenness according to energy consumption is fairly straightforward, and while that can’t capture everything related to embedded energy, building life cycle, etc., it is the sort of bottom line that anyone who can balance a checkbook can understand. And finally, we have a book that talks turkey about how do we get from being energy-dependent to a point where we’re more in control.

“Energy Free” manages to provide clear guidelines without being too dogmatic about any one thing. Edminster’s focus is on energy efficiency as a means to reducing our dependence on oil and other fossil fuels. Along the way, she exposes a lot of myths and misconceptions about what it really means to produce your own energy instead of relying on “the grid”. Although this approach is sometimes called Net Zero, she prefers to call it energy-free, because you’re freer, more liberated (to a point which YOU determine).  It’s both a manifesto and a guidebook for creating and enjoying a net-zero-energy home.

Determining That Net Zero Point

The first debunking is to explore what NZE means. For example, producing as much electricity as you consume onsite doesn’t take into account transmission losses from the power plant to your house. Also, you have to use different conversion ratios depending on the type of fuel you use (electric, gas, propane). In the case of electric power, the type of fuel used at the power generation plant can affect how “green” or “wasteful” that electricity really is. This forces the owner to confront his or her own principles at the get-go. How far are YOU willing to go and what will you get out of it?

Then there are practical questions about Net Zero. Will it actually save me money? Can I use the same builder? What are the real-world pitfalls and how do I avoid them? How do I manage the project? Who needs to be on the team, and when? Edminster does a superlative job of capturing the key drivers and human factors that can make your NZE project a success.

No One-Size-Fits-All Solution

Our culture of instant gratification and ever-shrinking attention spans does not lend itself to complex, thoughtful, tailored solutions. But, after clearly defining your principles, goals, and budget, the next thing you need to do is realize that every solution is local and is dependent on context. What works in San Diego may not make sense in San Francisco. And, concerns that are important for surviving a Massachusetts winter might not matter in San Jose.

A radiant barrier won't help as much in Tahoe as it will in Death Valley. Different climates call for different measures.

Edminster’s approach is to treat it like a team science project, and to keep everyone focused on the performance goals. It’s one thing to say that passive solar designs are nifty, but it’s better to start with some specific goal (and location), and then identify all the different ways one could achieve that goal. KNOW what your goals are, and be prepared to read the fine print – like which measures actually make sense for your climate zone. But don’t forget your personal goals, or you won’t be happy with the end result. A happy home takes more than just low-flow showerheads, and everyone on the team should appreciate this fundamental notion.

Your Team

This is something that other Green Builders have said, but it’s worth repeating, since we say it to our Title 24 clients as well. If you want a high-performing home, think farther ahead to make the best design decisions possible, and get your experts all talking to one another during the early design stages. And don’t use a compartmentalized series of handoffs, which unfortunately is the standard way of doing business in the homebuilding and home remodeling industry. Make sure your team members can work well together (that includes you) and that everyone starts on the same page. This is referred to as “integrated design”.

Green building requires a long-range planning approach, rather than a moment-to-moment response.

The skill sets are also different. A typical, non-integrated team might have an owner, a builder, and an architect. Other consultants might be brought in as needed but they have limited influence over design elements not in their immediate purview. They probably don’t have any visibility, either.

A compartmentalized, "handoff" approach might look like this Gantt chart.

In addition to the owner and builder, an integrated team might have a mechanical engineer, an energy modeler, possibly a structural engineer, and a renewable-energy vendor. All of these individuals need to be part of the initial design process, so that they can understand the wholistic impact of each proposed design element – and the reasons behind that impact.The team must have a clear common understanding of the goals of the project, in order to determine whether a particular impact is acceptable or not.

Start by Scoping Down Energy Needs

It makes sense once you hear it. Minimize the home’s energy budget before sizing any renewable energy systems. You do this by a multi-pronged approach that includes building, appliances, and occupants. The building should be efficient and not oversized; appliances should be not just Energy Star rated, but top of the chart; and occupants should be educated on things like how much energy a plasma TV REALLY uses.

Downsizing on floor space might be a hard pill for some people to swallow, but it’s really only going back to what homes were like in the 1950s, when the average was 292 SF per person. Now, it’s more like 961 SF – a threefold increase. Do we really need that floorspace? Or could some of it be outdoor space, or transitional space that doesn’t need conditioning?

This rather cramped attic is actually from Lawrence Welk's childhood home. A far cry from McMansions!

This Time, You Should Sweat the Little Stuff

Next come the appliances, lights, and electronics. What can you scope down or trade for a more efficient model? What can you eliminate? What energy management systems are there to monitor usage and to shut off appliances when not in use? What about water heating? Do you need that spa, or would a compact steam shower do almost as well?

Almost every item in the house offers opportunities for reduction, from faucets to lighting fixtures. For energy nerds, the lengthy discussions of just how much extra energy is used by the heating element inside your dishwasher will be glorious. But actually, everything discussed is in response to frequently raised questions about things like whether a measure really saves resources or not.

The section on building efficiency goes on for pages about different types of insulation, but even better were the detail sections showing sheathing, insulation, and airtightness. Everything from mold prevention to stack ventilation to solar heat gain. Without playing favorites, there’s a huge section on heating and cooling systems and how to get the most out of each type. There are even piping diagrams for hot water delivery.

But the best thing? An energy-modeling chart showing how the influence of different building parameters changes by building type and climate zone. For example, window area and solar heat gain was more important on the “urban” single family home in Palm Desert, but of lesser importance on a low-rise detached home in San Francisco. Surprisingly, building orientation did not have as much of an effect as one might think, except for the urban home in Palm Springs.

Living Patterns and Appliance Use

One thing I liked about the chapter on integrated design was the emphasis on behavioral factors and living patterns. For example, an owner who is away from the house much of the time might have different preferences than someone who is there all the time. Some owners may be willing to change their behavior or their tolerances as well. For example, foregoing heavy air conditioning in favor of the old Mediterranean tradition of afternoon siestas, or wearing a sweater on chilly mornings.

Putting on one sweater on a cool day might be better than immediately turning up the heat. But, if you have to wear a parka and frosbite protection indoors, the house is probably too cold.

As with HVAC systems, the discussion on appliances and their use is exhaustive. Everything from induction cooktops to dishwashers (including when to hand wash and when not to), gardens, gadgets, and monitoring systems. The only thing missing was the obligatory rant on the mercury toxicity of CFLs. (I personally feel OK about them – I can see better and they cost so much less to operate than my favorites, the halogens.)

Quality Construction

Even the fanciest windows won’t save as much energy if the builder does a poor job of installing them. The same applies to everything else: walls, systems, plumbing, ductwork. Each part of the whole should be optimized and well-crafted. Unfortunately craftsmanship is not a given for all builders, although they’d like you to think so.

Post Construction Verification

Much of the information presented in this book came from the author’s direct experiences. Just because an energy model predicted a home that uses 25% less energy, does that mean that the actual owners will use less energy once they’re living there? What if it’s too hot, or too cold, because of some factor or complex interrelation of factors unique to the site? What do you do then? Usually, with good planning, remedial measures will be minor, and can be anticipated, to be used only if needed.

Please note that we have no commercial interest in promoting Ann Edminster's book "Energy Free" - we truly think it's a great guide to planning your home energy strategy.

Don’t say we didn’t warn you. The new Title 24 is tough! In past articles, we harped on the HERS verifications as a way to earn credits towards Title 24 compliance for those hard-to-pass houses. However, there’s another angle that needs attention: issues for additions, alterations, and remodels.

(Above image shows a whole-house remodel and addition by Mark English Architects. Photo: Michael O’Callahan)

When does a remodel need to show Title 24 compliance?

When the changes impact the exterior building envelope, the heating/cooling/water heating systems, or when you’re adding conditioned area or volume. Envelope changes include new walls, replacing windows, and adding or enlarging windows. System changes include upgrading a furnace, changing the type of heating/cooling system, re-doing the ductwork, or upgrading the water heater. There are other circumstances like changing the lighting that may require Title 24 compliance. The focus is on conditioned space only, so garages and sun porches are not counted.

When do you NOT need a Title 24?

When all changes are internal and don’t impact the energy performance of the building. For example, if you move a group of interior walls but leave the furnace alone.

What are the methods of showing compliance?

There are two main methods: prescriptive and performance. The prescriptive method works just like a doctor’s prescription, with mandatory minimums for things like insulation or glazing performance. We do a little of that, but much of the time it’s fairly simple and many architects just do it themselves. The downside is that it’s less flexible – there are minimums, but it’s harder to get credit for exceeding those minimums in some areas in order to make up for shortcomings in others.

Not all remodels will qualify for prescriptive compliance. For example, if glazing is more than 20% of the floor area, or more than 5% of the glazing is on the west, then the project may need to use the performance method. The performance method is what we do, using a CEC-approved software modeling program.

How do I know if my project can qualify for the simpler prescriptive method?

You can use prescriptive compliance if your project matches all of the features listed in Table 151-C of the Title 24 Residential Compliance Manual, which vary by climate zone according to the 16 climate zones of California. (The Bay Area is mostly Zones 3 or 4 with some 2 up north and 12 out towards Sacramento.)

The prescriptive baseline values used for most homes are also known as “Package D”.

What is Package D and where can I find the documentation?

Package D appears to consist mainly of this one table, (Table 151-C) plus several pages of footnotes, which is tucked in the back of the Residential Compliance Manual under Appendix B. Even here not all the information is included; the table just says “MIN” for furnace AFUE for example.

What does the prescriptive method require?

The following is a very simplified summary. For areas like San Francisco, East Bay and the Peninsula, wood-frame walls must be minimum R13, raised floors R19, and ceiling/roof R30. Glazing U factors must be .40 or lower, gas furnaces .78 AFUE or higher, and air conditioners must be SEER 13 or higher.

The prescriptive method places strict limits on the amount of glass that you can add, especially on the west. For additions from 100-1000 square feet, glazing must be less than 20% of the conditioned floor area – no curtain walls, sorry. If you have an addition that is under 100 square feet, that portion can’t have more than 50 square feet of glazing. If the project is an alteration and no area is being added, glazing can’t be more than 20% of the total conditioned floor area. Some climate zones also specify that only 5% of the total glazing area can be west facing.

Medieval castles like this one had very low glazing-to-floor-area ratios.

So, if you want an addition with a glass curtain wall for your Esherick home, you will have to use the performance method.

I wasn’t planning on opening all the exterior walls. And I was going to reuse my old windows, too.

Don’t count on being able to reuse the windows unless they’re of fairly recent vintage. If your existing windows are single glazed, or clear glass instead of low-E, or they’re metal framed instead of wood or vinyl, you can forget it. All windows leak heat, but old ones leak a lot more. Keeping those old windows could easily double the energy budget for the entire home, which would kill your chances for Title 24 compliance.

For additions, alterations, or remodels, where only some walls, windows, or existing systems are upgraded, Title 24 allows several possible approaches or strategies. Again here, we’re talking mainly about the performance method, but these strategies are also available for the prescriptive method as well.

Obviously we can try modeling the project using the old windows, but we’ve ended up having to include a host of other measures to compensate – things like upgrading to a more efficient furnace, HERS-testing the ductwork for air leakage, even adding thermal mass.

What’s a HERS test?

Most of you know this by now, but HERS tests are third-party field inspections for things like duct leakage, and you can earn “compliance credits” for these tests when using the performance method to show Title 24 compliance. Running the software model with one or more of these tests specified can improve the score of the proposed design, sometimes dramatically. They require additional coordination during construction, but are not as inconvenient as having to spend an extra $15,000 on new windows.

For more details, see our recent article on HERS inspections and Title 24 compliance.

What’s the difference between modeling an Addition Alone or doing the remodel as a Whole House?

Additions can be modeled as self-contained if conditioned square footage is being added, the new space is all in one spot, and for modeling purposes it’s best if the addition is at least partially sealed off from the rest of the house. As long as you insulate all those walls, including new interior walls, and use efficient windows,  you can model this additional space as its own self-contained little building. This means you can keep the crappy windows in the rest of the house.

This proposed addition adds square footage and uses new windows, while the rest of the house is left un-altered. This project could use Addition Alone compliance method.

However, if no square footage is actually being added, then you can’t show compliance for only one corner, even if that corner is getting the royal treatment. This can happen if, say, a family room is getting a facelift and new windows, maybe bigger windows than before, but it’s staying the same size as before. At this point you have to either meet the mandatory minimums for the altered portion, including maximum glazing-to-floor-area ratios that may apply to the entire building, or you have to use the performance method, meaning you have to model the entire project within one of those approved software programs mentioned earlier.

It also happens sometimes that the Addition won’t pass by itself. If we have to use the performance method because of glazing area or whatever, we can try running the addition by itself. However, sometimes even the most thoroughgoing modeling efforts will not yield a passing score. Then we have to model the entire building (or condo unit) – and for that, we need to include information on all the existing exterior surfaces: walls, roof, floor, and windows. If the existing conditions are unknown, we have to assume the worst, based on when the house was originally built.

This proposed alteration is not adding new floor area. The main work is occurring towards the rear, including new windows and walls. However, there are also new skylights being added elsewhere in the house, and the front window is replaced with two new windows. This project would require the Whole House compliance method.

How does the Title 24 modeling software show a pass or fail score?

What the software model does is compare energy usage of the proposed design (your remodeling plans) with the energy usage of that same house assuming the mandatory minimums. Model inputs include the home’s compass orientation, wall areas, floor areas, roof areas, glazing areas, actual systems in place, and performance numbers for each. For example, a 1,200 SF home oriented at 90 degrees east might have 270 SF of north facing exterior wall insulated anywhere from R0 to R25. This would be compared to a 1,200 SF east facing home with 270 SF of north facing exterior wall insulated to the minimum, R13. Your design has to beat this baseline, shown in this energy use summary as the “Standard Design”.

This sample Title 24 compliance report shows energy usage breakdowns separately for heating, cooling, and water heating. If the house is not passing, it's easier to see where improvements should be made first.

I really don’t want to open any more walls or replace more windows, because that will put us way over budget! My clients will go ballistic! Why can’t we just add more insulation to the parts that are being opened?

If you have to model the whole building, then all the existing conditions have to be modeled as they are now. This means that if any of the existing walls are un-insulated, that house is going to have a very hard time passing the software model, even if the rebuilt portions are insulated far beyond the minimum.

It is sometimes possible to use blown-in insulation for existing walls without having to open them completely. We have found that even minimal insulation of all walls is far better than leaving any portion of the walls at R0.

So it’s not passing, what do I do?

At that point it’s a matter of incrementally testing in combination various additional measures that you may not have planned on doing. For example, if a house is ahead on heating but behind on cooling, then efficiency measures that aid cooling should be considered first. However, it’s also possible to achieve compliance through improvements to the heating system, even if the cooling is still below the minimum. That’s the advantage to using the performance method, and it’s sometimes the only way that highly glazed designs can pass.

If one measure isn’t available for a project, we can try others instead. Of course if there are too few alternatives – say they can’t afford to replace all the windows or they don’t want to get a newer, more efficient water heater – well, something still has to give. Resorting to elaborate workarounds in an effort to save money can introduce other risks into the project.

Yes, we feel your pain, too, but you still have to replace those windows.

What additional measures should I be prepared to consider?

Based on our own experience of 15 years doing Title 24 compliance for low-rise residential buildings, here are the findings that seem to hold true across projects.

Insulation. For remodels, do not leave any portion of wall un-insulated! This may not mean the entire house, unless we have to model it that way. Insulating to the maximum of what will fit inside the walls should be a given. This can include portions of the interior walls, too. (Radiant barriers are good in hot climate zones, but they don’t make much difference in San Francisco.)

HVAC. Upgrading heating, cooling, or water heating systems. This can be upsetting if the furnace is recent, but not quite recent enough. If your furnace has an AFUE of .90, but the project won’t pass unless that AFUE is .92, we have to deal with the situation as it is and find some way to address it.

For any remodel or addition project in California, additional measures may be required for Title 24 energy compliance. Clockwise from upper left: replacing inefficient windows, upgrading to more efficient heating/cooling/water heating systems, adding extra insulation, earning credits through HERS tests such as this blower door test, and finally, solar shading for homes that have problems with summer solar heat gain.

Windows. Replacing all or most of the existing windows. Obviously this can get expensive, and we try to avoid this. On one project we had to specify every HERS test there was, because they wanted to keep 5 existing windows that were metal-framed with clear glass. This project also had existing window that were wood framed with clear glass, but it was the metal ones that hurt the project the most. Poor window performance is the Achilles heel of compliance.

HERS verifications. We used to discourage the use of these third-party tests because it’s cumbersome to have to coordinate for yet another inspection during construction. And, there’s no guarantee that the test will pass on the first try, although there are ways to prepare for them to help things go smoothly. Now we’ve had to resort to them for about half our Title 24 projects.

Design changes. Our whole raison d’etre is to help architects comply with Title 24 without having to alter the design in a visible way. No shrinking of windows, no adding of south wall overhangs if the original design didn’t call for them. We’ll recommend product substitutions, but we’ve never had to tell someone that they couldn’t have their all-glass panoramic view. Still, I’m sure someday we’ll get a project where adding an overhang or side shading wall makes that 0.01% bit of difference between passing and failing.

Windows can leak heat in cold weather, but they also can admit too much solar heat gain on hot, sunny days, as shown in this illustration. The window on the left would be associated with higher cooling loads.

How accurate is the Title 24 software model? Just because a measure doesn’t help in the model, does that mean it’s really worthless?

Absolutely not! The Title 24 modeling software calculations are actually pretty thorough, although there are some intentional omissions that can, at times, make the building’s real-world performance quite different from what the model would predict. A home that in reality is covered by shade trees and a nearby mountain may show unrealistically high cooling loads in Title 24, because shade trees, adjacent buildings, and landforms are specifically not allowed as factors for compliance. I’m not going to get into the reasoning, but that’s how it is. Title 24 errs on the side of conservatism, so a house that does well in Title 24 should also do well in reality, even if the reverse is not always true.

What it’s good for is comparing the relative impact of one change over another. You can test the sensitivities of using triple glazed vs double glazed windows on just the west or south walls, for example, to see where you can get the most bang for the buck.

I don’t think the Title 24 software models are quite accurate enough to create energy budgets for things like Net Zero Energy homes, or to model temperature flows for passive solar designs. For one thing, appliances like TVs and computers aren’t considered at all, nor are differences in occupant behavior. It could give a rough cut analysis of major opportunities for optimizing the design, but then you’d have to move to something else.

Imagine a home built in the Plains region of the United States that stays warm in the winter without central heating, and cool in the summer without massive air-conditioning. It’s airtight but with an endless supply of fresh air constantly circulating through a filtered, pressure-balanced ventilation system. Every surface is comfortable to the touch, neither too warm nor too cold. Street noise is barely audible through the gasket-sealed, triple-paned windows. 

It sounds futuristic, but so-called Passive Houses have been around for at least 15 years, and it’s yet another strategy for saving energy. Unlike a Net Zero Energy home that might rely on “active” power generation, albeit from renewable sources, a Passive House is just that – passively absorbing heat from its surroundings to release it slowly as it is needed. (In hot climates, Passive Houses are designed to recover and store cooler temperatures.)

Passive House History

The idea of a “passive house” originated in Germany as a result of conversations between two university professors. A Passive House (Passivhaus in German) is a building that requires very little energy for heating and cooling, instead relying on passive energy sources and thermal isolation from its surroundings to achieve temperature stabilization. The notion began around 1988 and is now widely accepted in Germany and Europe. It’s now a standard, with specific and measurable performance requirements that can be field-tested and verified.

Buildings that meet the Passive House standard include public structures such as schools and supermarkets, as well as private residences. In the United States, the Passive House Institute US in Urbana, Illinois is a consulting and research firm working on adaptation and implementation of the Passive House standard within the United States.

This existing home in Ireland has been retrofitted to meet the Passive House standard, and yet it still looks just like every other house on the block. Designer: MOSART Architecture

Here in the Bay Area, Quantum Builders has become a recognized expert in the creation of Passive Houses tailored to our local climate. (Note that there is another builder of that same name in Texas, unrelated). An upcoming project in Tiburon is due to start construction this year, and was designed by award-winning architect Olle Lundberg of Lundberg Design. Bronwyn Barry of Quantum Builders spent considerable time explaining to me how it all works and showing me some of the wall assemblies that Quantum uses in their Passive House projects.

Wall details from above house showing "before" and "after" the Passive House retrofit, from the MOSART web site.

I also spoke with Jonah Stanford of NeedBased Inc., an architect based in New Mexico who’s a Certified Passive House Consultant with a successful track record of completed projects that employ advanced solar design principles in an artful and responsible manner. 

Passive House in a Nutshell

Passive Houses rely on an airtight envelope, lots of insulation, thermal mass, heat-recovery ventilation systems, and a thoroughgoing approach to slowing heat transfer through the walls that leaves no stone unturned. Wall assemblies tend to be thicker – in some retrofits, it’s like wrapping an additional blanket around the existing house – but the most unusual thing about the walls apart from air tightness is the extreme attention paid to eliminating thermal bridging. “A typical home can lose 25% of its heat from thermal bridging,” said Bronwyn.

Thermal bridging can be responsible for 30% of heat loss from a home. Wood frame studs have a lower insulating value than the batt insulation between them, and if the studs are directly in contact with the inside and outside of the wall, they can act to conduct heat out on cold days, resulting in unwanted heat loss.

In a way, it’s not unlike NASA sending up a manned spacecraft and having to account for every last gram of weight, to ensure that there’s enough fuel to get it to its destination. The interior has to be kept warm enough to keep out the cold, which is a chill far more extreme than anything you’d find on the Earth itself. And of course, manned spacecraft have to be airtight, because any air leakage at all would be disastrous.

The idea with a Passive House is to stabilize temperatures by making the thermal mass of the house work for you like a giant hearthstone. You don’t need a conventional furnace at all – even in Northern Europe! Once the house is at the desired temperature, it takes very little energy to keep it there. “Improving a home’s airtightness can result in 25% energy improvement,” said Bronwyn.

Passive Houses have been built in every climate zone. Desert climates of course are more concerned with keeping cool by managing solar heat gain, whereas cold-winter areas are more concerned with staying warm. Tailoring the design for the specific climate and site conditions is of paramount importance.

Clockwise from upper left: Crossway House by Hawkes Architecture in the U.K.; Breezeway House in Salt Lake City, Utah by Brach Design Architecture, the first certified Passive House in the U.S.; zero-emissions research station in Antarctica.

(Note: I’m not sure that they are all “Passive House certified” but they all use the basic Passive House principles. Breezway definitely is certified, and Crossway is “zero carbon” home that has also been accredited by the Passivehaus Institute in Germany. Bronwyn mentioned the Arctic research station as a Passive House, so maybe it’s actually certified as well.)

The Passive House standard doesn’t specifically require the use of non-toxic materials, although the wall assemblies that I saw used materials that were carefully chosen partly for low toxicity – cellulose and rock wool insulation, wood and low-toxicity oriented strand board. Off-gassing isn’t as much of a problem as I had originally thought: the ventilation system has a low but constant rate of air exchange that doesn’t allow stale air to accumulate anywhere in the home. Passive Houses are credited with having excellent indoor air quality; that’s one of their selling points.

Humidity also has to be managed, as with other tight-envelope buildings. Placement of vapor barriers is dependent on climate, similar to other types of construction. The wall assemblies at Quantum Builders showed extensive attention to waterproofing as well as the placement of air and vapor barriers.

Rafter detail showing vapor barrier at interior (blue,) air-barrier at existing siding (red) and bulk moisture barrier at roof sheathing (red.) Arrows show air movement within the roof assembly, allowing air to escape from vents in the roof for passive cooling. Taken from a study for a Passive House retrofit by Quantum Builders.

Like other standards, a Passive House building performance analysis includes the creation of an energy budget. Energy budgets are a key component of many other energy-saving approaches and standards such as passive solar design, GreenPoint Rating, HERS home energy audits, Net Zero Energy homes, or California’s Title 24 energy standard. The Passive House energy budget is thorough and detailed, including occupants, appliances and lighting. Both power consumption and heat generation are considered. 

How do Passive Houses differ from, say, Passive Solar or Net Zero Energy homes?

Passive House is more than a set of principles – and it’s more than a checklist. Passive House is a formalized approach with an associated standard, modeling software, energy budget, and certification/testing process. To be fully certified, each Passive House is verified against actual building performance after the building is completed, as follows:

1. Heating and cooling demand is less than 4.75 kBTU per square foot per year. (A regular house might use 15 times that amount.)
2. An air-tightness rating of less than 0.6 air changes per hour, measured at 50 Pascals. 
3. Energy demand for all uses (called “specific primary energy demand”) including hot water, heating, cooling, auxiliary, and household electricity is less than 38 kBTU per square foot, per year.

The Passive House performance standard.

By comparison, passive solar design isn’t really a “standard” that can be pass or fail. The passive-solar approach looks at building orientation and other principles of solar design, but there’s no specific energy modeling software associated with it (although many software programs can be used to assess most of the solar gains, etc).

Net Zero Energy homes don’t really have a standard or certification other than daily use. They do have a performance goal: use less energy than you produce within a single year, with an annual reckoning every December between you and the utility company. If you’re grid-tied and your energy bill for the year is zero, then yes, you produced more than you consumed, so the house is Net Zero – at least for that year. But there’s plenty of synergy among these approaches. “Passive House gets you super-close to Net Zero Energy”, says Bronwyn. “If you meet the Passive House standard, then Net Zero is easy.” A Passive House requires less energy to begin with, so you’d be able to reduce the size of your renewable-energy systems accordingly.

Title 24 does provide good baseline performance measures, as Bronwyn explained. “The R value needed to meet the Passive House standard varies by climate and is determined per project using the Passive House Planning software. In Minnesota, you might need R30 to R40 walls and R50 roof. Here in California, a Passive House should have around R21 walls, R11 insulated slab, R28 roof, and really great windows.” By comparison, Title 24 mandatory minimums are R30 roof, R13 walls, R19 floor, and Low-E windows. 

The differences lie in the root of each strategy. 

• Passive House is about temperature stabilization as the main focus for reducing the need for actively generated power. 
• Net Zero Energy is about achieving a “net zero” balance between onsite power generation and power consumption, with a strategy that includes active power generation through solar, wind, or other renewable energy sources.
• The GreenPoint Rating system focus is on long-range resource conservation, energy efficiency, community design, and environmental health. So does LEED.
• They all differ from Title 24 in that you can factor in your shade trees for credit, or include these features as part of the energy model.

Tell me about energy budgets in Passive Houses.

Part of the Passive House standard involves setting a specific overall energy budget for the home based on “treated floor area”, or conditioned square footage up to the interior wall area. The Passive House energy budget is imposed purely based on size regardless of activity, and includes all appliances, not just heating and cooling. It’s up to the owners to decide how to use that budget. It’s challenging to meet the standard, but definitely possible. Typically, you have to be very careful when selecting appliances. The Energy Star rating only sets a minimum efficiency; within that, appliances can vary widely in how much power they actually use.

The Passive House software tool, called the Passive House Planning Package, is an elaborate Excel spreadsheet that helps to create a detailed energy model of the home. Although use of this tool isn’t strictly required, it seems to cover every possible angle and takes all the Passive House principles into consideration.

What if you want to light a couple of candles over dinner? Will this throw the house off?

A good ventilation system can take that into account. What most owners do is they open a window! But yes, you do have to be aware of every heat-generating activity that you do. However, Passive Houses can accommodate a wide variety of activities and lifestyles. You don’t have to be afraid of exercising in a Passive House or of hosting large groups of people. In Germany there are entire kindergartens and office buildings that are Passive House certified, even an indoor pool!

What happens if you leave for a long weekend and forget to take out the trash?

The first question everyone asks when they hear about a hermetically sealed, airtight house is “What happens if you fart indoors?” Even though the question itself is crass, the concerns about stale air are reasonable enough, given all we’ve heard about airless offices and flu-laden airliner jets.

“Passive House ventilation systems usually have a ‘flush’ feature nowadays,” said Bronwyn. “If you need to clear the air, you can activate this cycle and then the system resumes normal operation.” As with the above question, you can also open the windows for 10 minutes, air the place out, then shut them again without seriously disturbing the temperature balance inside the home. 

Passive Houses have better air quality than so-called normal buildings. Bronwyn and I spent time discussing the chronic health issues so many urbanites face, from asthma to migraines. She quoted me longitudinal studies from a school in Germany that showed reduced absenteeism, improved occupant health, increased attention span, and reduced CO2 levels. “In a Passive House, the indoor air is constantly being filtered and circulated, while stale air is constantly being expelled.”

Can you use carpeting inside a Passive House? Are there certain conventions for indoor furnishings and materials that need to be re-examined?

Yes, you can, and any dust it generates will be less of a problem because airtight houses are less drafty. There are no stray air currents to kick up dust into the air. There is no reason why you couldn’t use all the same interior design techniques that you would in any other home.

What’s it really like inside a Passive House?

I asked this question of Jonah Stanford. “It’s like being on the moon,” he answered. “It’s amazing, really. The house acts totally different in some ways from what we’ve been conditioned to expect. If you stand near a window on a cold day, you won’t feel a thing. Normally you would feel a thermal draw from the window in cold weather.”

A cross section from a window designed using Passive House principles. It features argon gas-filled triple glazing, thermal breaks, insulation inside the frame, full gasket seals at three places inside the frame, and a waterproofing system on the outside to trap and guide rainwater out and downward.

The evenness and stability of the temperature inside a Passive House eliminates hot and cold zones that we may be used to. “I went to a 2 story office lobby that used Passive House principles and we measured the temperature at the floor, the wall, and the roof. It was all exactly 21.5 degrees Centigrade. Phenomenal.”

Do occupants feel separated from the outdoors?

Not at all. Passive Houses are quieter, but they actually have more fresh air. Occupants can open windows when it’s nice outside as much as they want, just as they would in a conventional house. The only differences is they don’t HAVE to.

Does the Passive House standard REQUIRE that you purchase special building materials all the way from Germany? Can’t you do it using local materials?

Yes you can. Quantum has chosen to work with German manufacturers because they’ve got more experience building to the Passive House standard. Importing assemblies from Germany to the Bay Area actually uses less embodied energy than, say, trucking them from Minnesota. Apparently to be really “carbon compliant” everything trucked by surface has to come from a distance of under 300 miles. 

It’s not the materials, it’s the details that have to be reworked. All thermal bridging must be eliminated, which requires special measures. In addition, airtightness, vapor protection, and waterproofing all need to be addressed.

Insulated roof ridge detail before and after, showing how R-values were improved from a mere 2.2 up to R-50. Taken from study for a Passive House retrofit in Larkspur, by Quantum Builders.

There are no books on typical detailing for Passive Houses – yet. Builders on the East Coast can often use details from German books on Passive Houses, but these details are optimized for a cooler climate and rely more on masonry than on wood frame construction which is most commonly used here in California.

Aren’t the floors cold? Is every surface supposed to be the same temperature?

There is slab insulation under the home to keep the floors from leaking heat out into the ground. A Passive House has a lot of thermal mass partly to keep every surface temperature constant. Thermal imaging via a software package called THERM is a useful supplementary tool. Bronwyn showed me two thermal images, similar to the example image shown below, comparing the effect of placing slab insulation either above or below the slab. 

Imaging example showing a thermal model of a floor to wall assembly, from the software package THERM. Image courtesy of Quantum Builders.

Although both floor surfaces were warm where the floor met the air, the warmth went deeper when the slab was exposed and could warm itself. With the slab underneath, it sucked cold up from the ground and stayed that way.

How NOT to design a foundation. This shows how thermal bridging can effectively drain all the heat out of your home.

What does the ventilation system need to do?

For a Passive House, you need a good mechanical heat-recovery ventilation system with balance between air intake and exhaust, delivering 0.6 air changes per hour. The house should have an even pressure balance between inside and outside air. Air filtration components may be selected based on the location and occupant needs, but are always present. Special attention is paid to the location of openings for air intake, which may vary by climate as well as site. For example, intake in very cold climates may require some form of pre-heating via earth tubes.

“HEPA filters aren’t always necessary,” said Bronwyn. “Passive Houses have lower airborne particulates already, because there are no indoor convection currents (drafts) to stir up dust. The fact is, so-called ‘normal’ indoor air quality is poor to begin with.” 

What additional costs are associated with building a Passive House as opposed to a “regular” one?

The Wikipedia article on Passive Houses contains the statement that overall, Passive Houses cost on average 14% more to build and are more expensive in Northern latitudes above 60 degrees. Other sites claim 10% overall or 7% in Germany. I didn’t get a figure from Quantum, although it’s clear that the additional insulation and thicker walls do add somewhat to the cost. 

“It’s really important to have a fully committed client,” said Bronwyn. “Otherwise they may not want to go all the way.” I observed that most people don’t view their houses as legacy homes to be handed down to their children. It seems that most people stay in their homes about 5 years or so and then move on. They’re not as willing to invest in improvements that you can’t see.

Do Passive Houses have a thermostat?

Yes. Typically this would be set to 68 degrees, and is adjustable to suit occupant preference.

Can you have multiple heating zones for sedentary vs vigorous activity?

If you want to have a small office that’s nice and warm, while the rest of the house is at a cooler temperature, you can use a small portable space heater. This can be accounted for in the home’s energy budget during the early planning stages.

How well do Passive Houses do in extreme climates?

There are Passive Houses built in all seven climate zones in the US. There’s even one in Antarctica, a research station. A desert Passive House will be geared more towards cooling, but the actual wall assembly is similar to what you would use in Minnesota, in both cases well-insulated and protected against thermal bridging, because in either case you want to minimize thermal transfer through the walls.

This desert home by Kendle Design is not Passive House certified, but it uses the same principles of solar design that would also be employed to build to the Passive House standard: massive earth walls and solar shading. It might be challenging to make a glass wall this large using the airtight, triple-paned construction details shown on other Passive House windows, but who knows?

Within the U.S., the most challenging climates seem to be the cold regions around the Canadian border, and the extreme heat and humidity in places like Florida and the Gulf. Sometimes the use of geothermal or earth warming tubes buried in the soil can act as heat exchangers to pre-heat or pre-cool outside air before it goes through the ventilator.

Let’s talk about special building techniques for Passive Houses.

The Passive House standard is performance-related rather than material-specific. Quantum Builder’s South African case study is 100% predesigned and prefabricated from custom-produced wall and roof assemblies. In the Ukraine, according to Jonah Stanford, there are Passive Houses built with monolithic wood walls, although I wasn’t able to find any immediate specifics online. Regardless of material, airtightness, moisture management, and the elimination of thermal bridging are important considerations when designing specific wall assemblies. 

What’s inside this wall assembly here in your office?

From inside to outside: 

1. Drywall
2. Furred-out mechanical chase
3. Oriented strand board layer for air-barrier & structural sheathing
4. Cellulose between the structural framing
5. Insulated fiberboard impregnated with wax
6. Rain-screen furring 
7. Exterior siding

One of the wall assemblies on display at Quantum Builders' offices.

What about the windows in a Passive House?

The one component that isn’t easily obtainable here are the windows. Windows that meet the Passive House standard are hard to come by. They must be airtight, triple glazed, with insulated frames, with a very low U value – .14 or even as low as .11. All moving parts must be precisely fitted, like airlocks in a spaceship.

“R values of typical window are poor. A typical vinyl window is around R2, and the best Marvin windows are around R3.2. The R value of a Passive House window needs to be more around R7 to R9,” said Bronwyn. Considering that the minimum wall insulation in CA is now R13, the windows present the primary avenue of heat loss in a home, and it pays to make them as thermally efficient as possible. Installing the windows presents an opportunity for further insulation. In some cases the window frame can actually be layered behind additional insulation extending from the walls of the house.

The thermal performance of a window is influenced by the performance of the frame, the glass, and the spacer. In addition, the installation method can affect the performance of the entire wall. Each of these components within a window should be as thermally efficient as possible.

Bronwyn had special words about vinyl windows. Although they’re encouraged in Title 24 as being efficient, they have a reputation for off-gassing. And they’re still not airtight enough. The windows used by Quantum are made from wood, sometimes with aluminum or fiberglass cladding. The fiberglass clad windows are enhanced with a special insulating foam: Neopor- a super-insulating carbon impregnated type of EPS, on the outside of the window.  Any gas that escapes can’t penetrate the air barrier to get inside the house.

If you import special materials and such, do these products meet local building codes and standards?

I was especially interested to know if the imported windows were NFRC rated. Bronwyn informed me that their window manufacturers were in the process of getting their products rated, which can take up to a year. 

Why would you choose to go with the imports rather than building it locally, then?

Passive House materials must be built to the most exacting standards possible. Air-tightness must be controlled at every joining, every assembly, every switch box. Rather than try to manually assemble everything onsite, it can be both faster and more quality-enhancing to produce components such as wall systems in a factory that is already set up to achieve these standards. Having vendors and suppliers you can really rely upon is vitally important. Right now, most of these factories are in Germany because the Passive House standard was originated there, by building scientists, with strong support from the German government.

Quantum Builders already had strong ties with Germany, and has chosen to work with factories that achieve precision and who are committed to using high-quality, non-toxic products. These producers offer custom details as well as a wide range of standard products to satisfy design-oriented architects.

Jonah Stanford confirms that Passive House standard does not mandate a particular type of material, only a specified performance threshold. “The German assemblies that Quantum uses are actually quite reasonable in terms of cost. We’ve also price-compared both the German imported assemblies versus site-built or prefab assemblies made locally, and it came out about 20% less than importing – basically the cost of shipping.” 

When building manually, you have to pay a lot of attention to thoroughly sealing all electrical and plumbing penetrations, to keep the vapor-lock tightness. “You have to be obsessed with it, and even so, the seals might not last as long as the building,” says Stanford.

Stanford is working on his own assembly, a double stud framed wall. What distinguishes this wall from a “normal” wall is the layering. “The interior wall is load-bearing. Then, I use oriented strand board – NOT particleboard, followed by another layer of studs that are not vertically bearing.” This idea was, he says, inspired by the Ukranian wood frame Passive Houses, which are literally built from the inside out. 

There can be conflicts with local codes or incentives. In NM the incentives are generous, but require adherence to ASHRAE Standard 62 which requires outside venting for appliances like dryers. In a Passive House, however, the heat from that dryer should really be kept inside the house, at least in the wintertime.

What special skills are needed to design systems for, and actually build, a Passive House? 

Bronwyn had a couple of thoughts on this. The first was to have an integrated team from the start. “Architect, owner, builder, energy analyst, structural engineer, mechanical – they all have to review the early drawings together,” she emphasized. The second was to produce good construction drawings and details. “If the details are clear, any builder should be able to build to them – as long as they understand the why.”

Can an existing home be remodeled to meet the Passive House standard?

Yes, although some details such as under-floor insulation, strongly encouraged in Passive House construction, can be difficult to retrofit in existing slabs. Bronwyn showed me some details for Quantum’s remodel project in Larkspur. 

Although the added thickness does increase the home’s footprint very slightly, this in and of itself is not a problem unless the home is on an urban lot right up to the property line. In that case, the retrofit might have to concede a little space on the interior.

For the roof, you might have to actually raise the roof in some cases, in order to create additional room to fit the necessary amount of insulation. In jurisdictions where they might be picky about adding 6 inches to the building height, you might have to build down or lower an interior ceiling.

Isn’t rigid foam toxic, though?

During the roof discussion, Bronwyn and I got into a side discussion of different insulation types and R values, which is a measure of the resistance to heat transfer (higher is better). Typical batt insulation has an R value of around 3.7 per inch, meaning you can fit up to around R13 into a typical 2×4 framed wall. However, some types of rigid foam insulation can do better. Polyisocyanurate, for example, has been claimed as being R8 or even R11 per inch. I’d been wondering about the toxicity of this – “polyisocyanurate” just SOUNDS toxic!

Bronwyn pointed out that in the case of the roof assembly, the foam is on the outside of the air barrier, and the polyiso isn’t the worst thing out there. Formaldehyde from conventionally made engineered lumber products is a LOT worse, lasts a lot longer after installation, and it’s ubiquitous in buildings already.

What happens as part of the Passive House design and certification process?

The steps to Passive House certification are as follows:

1. During the schematic design phase, use the software to determine which wall assemblies (R-value) will meet the Passive House standard for the particular project based on climate. From there, you can proceed to create a detailed energy model of the project including surface areas, ventilation, windows, shading, even prevailing wind speed. It is essential to have input from your design and build team during this refinement. When design is complete, the drawings and the project modeling file are sent to the Passive House Institute US for pre-certification prior to construction. This takes around 4-6 weeks and costs around $800.
2. During construction, a third-party inspector comes out to verify that the house is actually built to the drawings.
3. After construction is completed, a third-party inspector conducts an official blower door test, to verify that the home is airtight. This test can be done by a HERS rater, as long as that person knows how to test specifically to the Passive House standard. This includes verifying a neutral air pressure balance inside and outside the home.
4. The final step in certification is to re-verify the home against the as-built drawings. This takes another 4-6 weeks and costs an additional $300 depending on complexity and size of the project.

As Bronwyn noted earlier, special attention should be paid to construction detail drawings. Construction Documents are one phase that sometimes gets short-changed, because clients mistakenly believe that it will “save them money” – and then those details get worked out in the field by the builder. With a Passive House, you can’t do this because those detail drawings will be required for verification during construction.

What do architects need to know in order to design a Passive House? Would they work with a special builder or consultant to do the modeling?

Jonah Stanford mentions that you have to design to the Passive House standard from the beginning of the project, which would seem obvious but it’s worth pointing out that if you start out designing a standard home (or standard remodel) and you’ve already gotten as far as construction drawings, and THEN you decide to meet the Passive House standard, you will have to re-do all the wall assemblies. Expensive. “You can’t change horses in the middle of a stream,” I said, to which Stanford responded, “No, it’s more like switching from horseback riding to driving a herd of pigs through the water.”

How did you choose Lundberg Design for a passive house project? 

There was a long and careful selection process, where we interviewed several architects.

This straw-bale house, also built by Quantum Builders, isn't a certified Passive House, but it uses passive solar design principles, and it's quite a nifty shape.

What’s the response from Planning to your project?

They’re fully behind it – as long as it still complies with the building code.

A few months ago we published an interview with a GreenPoint Rater to de-mystify the GreenPoints system that was suddenly taking California building departments by storm. Like LEED and several of the current rebate programs, GreenPoints has tie-ins to Title 24′s energy compliance scoring, and so we’ve had to help our clients to interface with this new standard.

There’s another standard that’s been around for a long time – the Home Energy Rating System, or HERS. For the first time, we are having to tell our clients that they will have to do at least one HERS verification in order to meet the new 2008 standards of California’s Title 24 energy code. Suddenly, everyone had questions. What in the heck do HERS raters actually do, and what does it cost? Is this going to be a huge headache or a minor annoyance? What benefit is there to HERS testing apart from compliance? What does a person have to do to become certified as a HERS rater?

I’d make a distinction between green-building standards and energy performance standards.

• Green building is focused on the bigger picture, on quality of life, and on the entire life cycle of the building and possibly the surrounding community. Examples include LEED and GreenPoints.
• Mechanical/efficiency standards are focused on building operational performance and energy usage. In this context, the Home Energy Rating System, or HERS, falls into this second category.

What HERS raters do is make your home more energy-efficient by auditing its current performance levels and pinpointing areas of poorest performance. A few weeks ago, I looked at the CEPE roster shared by the California Association of Building Energy Consultants (CABEC). I was looking for people with dual or triple credentials in GreenPoints, HERS, and as a Certified Energy Plans Examiner (CEPE), since those are the three areas where we most often have to interface with our Title 24 work. One of the people listed on that site, Rob Lehman, is the subject of today’s interview. Rob is also listed on our Affiliates page.

In the text below, Rob’s answers are credited as RL, and editorial notes are shown as [bracketed italic].

What do HERS raters do exactly, and why is it important?

RL: HERS raters are special independent inspectors certified through a HERS provider, and ultimately by the California Energy Commission (CEC) to evaluate homes in California according to the Home Energy Rating System (HERS). These ratings include field verifications and diagnostic tests to determine existing efficiency levels for various energy-consuming components such as:

• Heating and cooling systems
• Supply and return air ducting
• Building envelope air infiltration
• Building envelope insulation quality

A HERS rater will also perform a comprehensive energy analysis of the home, including energy consumption for all daily living activities in the home. This evaluation includes the heating and cooling systems, and how the building components such as insulation, doors, windows, water heater, and lighting all affect the home’s energy efficiency. The information is entered into a computer program that calculates an energy rating for the home. All of the possibilities for improving energy efficiency are analyzed and prioritized according to which ones provide the most improvement relative to their cost.

This illustration shows where the bulk of energy loss occurs within a typical home: 40% through the roof, 36% through the floor, 14% through the walls, and the remaining 10% through window and door openings.

[HERS is nationwide, not just California. The California HERS program was implemented starting in 1999, and is used provide field verifications for energy efficiency programs. HERS Phase 2 or HERS II is the next stage in that implementation within the state of California. There is also a national HERS program sponsored by the Residential Energy Services Network (RESNET).]

How did you get into this work?

RL: I became interested long ago in do-it-yourself energy conservation and efficiency through Mother Earth News way back in the 60′s and 70′s, and dreamed of a day when smarter building methods would actually be used to conserve energy and help to save the environment.  When I realized the opportunities were out there to become a HERS rater, I joined right away. I have always dreamed of having an active and productive part for myself in energy and environmental conservation efforts.

Where can people find a HERS rater?

RL: People usually come to me through their builders. The public hasn’t caught on yet where to ask for Home Energy Rating Systems inspectors, but you can find HERS professionals listed on sites like CABEC, or through one of the three registered HERS provider organizations within the state of California:  CHEERS, CalCERTS, or CBPCA.

For our market space – residential low-rise Title 24 – what are the most common verifications solely for Title 24 compliance?

RL: The most common HERS verifications that I have performed for low-rise residential construction include tight duct tests and Quality of Insulation Installation, or QII. That’s my advice – start with the ducting and the building envelope.

A blower door test measures the amount of air infiltration within a home.

Some other HERS verifications that are also good to do, and which earn compliance credit within Title 24, include:

• Blower door test for air infiltration through walls, ceilings and floors
• Refrigerant charge management and verification in split system air conditioners and heat pumps
• Measurement and verifications in a/c cooling coil airflow
• Measurement of air handler fan watt draw
• Verification of high energy efficiency ratio (EER) for the air conditioning system, through component matching
• Visual inspection of supply duct location, where ducts are located within conditioned space
• Visual inspection to verify buried ducts or deeply buried ducts
• Photovoltaic installation verification

To qualify for Title 24 compliance, all of these measures require a certified HERS Rater to conduct a field test or visual inspection, and register the results with a HERS provider.

[A HERS provider is not a person, it's an organization such as CHEERS, that is certified by the State of California. You can earn compliance credits through HERS verifications if you use the performance method of Title 24, which employs a software model to simulate the building's energy performance.]

As time goes forward, I believe that people will have to use HERS verifications more and more, as a bolstering measure for Title 24 energy compliance. They will need the extra credits from the HERS verifications to obtain the Title 24 performance scores necessary for green building certifications such as LEED, Build it Green (GreenPoints), and Energy Star.

Are you finding that it’s harder to get projects to comply under the 2008  Title 24 code? What sort of measures are you having to advise your clients to take?

RL: Numerous changes within the 2008 Title 24 energy code have raised the standards for higher energy efficiency in California homes to roughly 15% above that of the 2005 energy code.  And this is just to obtain a passing score of “0″. All this is being driven by AB 32, the Global Warming Solutions Act of 2006. The State of California will continue to tighten up requirements in future code cycles, which happens every 3 years.

I advise my clients to take advantage of the HERS verifications that will help them the most, within their climate zone. In San Francisco, there isn’t a tremendous demand for cooling such as there is in Fresno. So perhaps instead of recommending a refrigerant charge management test, I might recommend a blower door test for whole house air infiltration, to identify problems with a poorly performing building envelope.

California has 15 climate zones, each with different heating and cooling loads. For example, San Francisco is Zone 3, San Jose is Zone 4, both relatively moderate. Livermore, which isn't that far away, is Zone 12 - much hotter.

I have found that including even one HERS verification yields a very significant improvement in the Title 24 energy report score. If the client plans on obtaining a green building certification through a program like GreenPoint Rated or LEED, a Title 24 performance score of 15% better than “0″ is mandatory.  Considering that the 2008 Title 24 requirements are already 15% tighter than before, plus the additional 15% over baseline required for Build it Green or LEED, it is easy to see that employing a HERS rater may be essential for achieving all these goals.

Compliance aside, what are the most worthwhile verifications or services that a HERS rater can do? Why would someone hire a HERS rater aside from Title 24 compliance?

RL: Saving energy! That translates into lower utility company bills, month after month. Everything that a HERS rater can do is an avenue for improvements that will save money. Here in the Bay Area, I recommend starting by investigating the building envelope and duct systems.

A duct blaster test in progress. This duct lying on the floor looks a bit like a python at the zoo.

I recommend starting with the ducting because the standard methods of installation for HVAC ducting throughout the years has not been favorable to tight, efficient ducts that have low air leakage. I’ve heard figures quoted in training workshops stating that 30% leakage in a typical ducting installation is routine, and the air infiltration even in some newer homes is still very poorly controlled. That is a tremendous waste of valuable heating or cooling BTUs! All that expensive conditioned air could be going into the attic or under the crawlspace, or out through holes and gaps in walls, floors, and ceilings and not into the home where you want it.

That’s crazy! Are ducts really that poorly installed every time?

RL: Duct leakage is an issue especially in tract homes that are built by contractors working under the gun to finish the job as quickly as possible. Another problematic practice has been that the so-called “standard” for duct sealing for many years has been to use duct tape for sealing the ducting to the sheet metal connectors. But, most duct systems are in the attic, which get as hot as 140 degrees in the summer time. Duct tape adhesive isn’t designed to withstand these temperature extremes, and it dries out.

Ducts, plenums, air handlers, and connectors should be sealed with mastic on all joints and seams.

OK, so tract homes are one thing, what about custom residences? Do they have leaky ducts, too?

RL: Even in custom-built homes with higher standards of care, it still happens. The standards say not to depend on duct tape, that instead duct mastic should be used. [Mastic is a high-strength flexible adhesive that can tolerate temperature fluctuations.]

Don't use duct tape to seal your ducts - use mastic. There are plenty of web sites to show you how, although if you've never done it before, consult a professional.

What is Title 20 and why do HERS raters care about it?

RL: Title 20 is a piece of California legislation that empowers the California Energy Center to approve the software and protocol necessary for HERS II Raters to conduct energy audits, in order to tie those audit results more closely into various new incentives. There have been energy-auditing businesses and HERS provider organizations offering their services for years now, but until now they have not been regulated by the State. One reason to do so now is the increasingly complex interrelationships among the various energy-related incentives, rebates, and tax credits with Title 24′s energy compliance scoring system.

Title 20 is new legislation, very recently passed in California, which is now in the implementation stage. My HERS Provider, CHEERS (which stands for California Home Energy Efficiency Rating System) is within one month of being available to train and certify HERS II Raters to audit and report energy scores for various incentives, rebates, and tax credits.

Are there other pieces of legislation in the works that we should know about?

RL: Local government financing of homeowner energy improvements through AB 811 may require a HERS II Rater to perform various tests to show how much energy efficiency improvement has actually been achieved. The Federal Home Star Program may require similar verifications.

Rumors of mandatory energy score reports for real estate transactions when selling a home in California are probably not going to pass as law anytime soon, because there has been a lot of opposition from the real estate lobby.

What do general contractors and HVAC contractors have to do differently now under the new Title 24 requirements?

RL: If there are required HERS verifications for any portion of the scope of work involved for a permit, General Contractors and/or HVAC Contractors will have to hire a HERS rater who will register the HERS verification measures online in order for the contractor to obtain a building permit. This requirement will take effect October 1, 2010.  The documentation for the HERS verification (included on the CF-1R Title 24 report) must accompany the application for the building permit, and be submitted to the building department for that jurisdiction.

[These HERS verifications consist of whatever tests were called out originally on the Title 24 report also known as the CF-1R, which was submitted earlier to the planning department for site permit.]

In terms of the CF-1R and CF-6R connection, who’s responsible for what? Where is this all-encompassing HERS data repository, anyway? Who owns and maintains it? How can an architect look up the status of his or her project to see if the project was properly registered? If the HERS rater doesn’t follow through on the reporting, what does the architect have to do to follow up?

[Each registered HERS provider maintains its own separate online registry. Again, these providers are organizations, not people. There are three HERS providers in California: CHEERS, CalCERTS, and CBPCA. Ask your HERS rater which provider he or she is certified through to discover where your project will be registered, and check that provider's web site.]

RL: There are actually three compliance-related forms for Title 24 now: The CF-1R, the CF-4R, and the CF-6R.

• The CF-1R (the Title 24 compliance report) indicates which HERS measures have been specified for credit in the Title 24 energy calculation. Both the architect and the project coordinator are responsible for knowing what is on the CF-1R in terms of how the building and systems are modeled, including specific performance data for products such as furnaces and windows, and any HERS verifications that are specified. The architect should communicate this information to the other parties for follow-up as the project schedule requires.

• During the course of construction, the owner of the project, or his or her contractor, is responsible for ensuring a successful verification by a HERS rater for each measure listed on the CF-1R.

• To prepare for each HERS verification, the contractor (general, electrical, solar, or mechanical) furnishes the HERS rater with a CF-6R, describing the portions of their work or installation that need to be verified. This could include ducting, an HVAC system or component, solar photovoltaic arrays, or insulation in the walls, floors, or attic.

• The HERS rater is responsible for performing the verification and registering the results (pass or fail) with his or her HERS provider’s online registry within four days of performing the test or inspection. These results are also known as the CF-4R report.

• The building inspector (building, electrical, mechanical) is responsible for collecting documentation certifying that the HERS verification is complete, approved, and properly registered before signing a final inspection.

What’s the best way to ensure that the tests happen at the right time during construction?

[The general contractor or construction manager should do the following:

1. Make sure that they have accurate information about the HERS verifications that are required for the project, and
2. Include both the HERS verifications and any pre-testing at the appropriate time in the construction schedule.

For example, the ductwork can be pre-tested prior to completion of construction, but it will be an extra task for the contractor to do so. Since most contractors do not own the duct testing equipment themselves, they may need to have another HVAC professional (the HERS rater can't do it) do some pre-testing prior to the "official" test, at a time when the ducts are accessible for additional repair if needed. However, if the contractor waits for the official HERS test and the ducts don't pass, they may have to pull off sheetrock in order to address and repair any deficiencies.]

Let’s go through each of the tests individually and describe what’s involved.

What happens during a duct blaster test?

RL: Also known as a verified air leakage test, a duct blaster test is designed to test and document the air-tightness of forced-air duct systems. It takes about 1 to 2 hours to do.

Why is it that the only photos I could find of duct testing all show men?

In this test, the HERS rater attaches a calibrated air flow measurement system directly to the duct system in a house, typically at a central return, or at the air handler cabinet. With the remaining registers and grilles temporarily taped off, duct air tightness is measured by either pressurizing or depressurizing the duct system and precisely measuring the fan flow and duct pressure. The findings result in a percentage of leakage for that system.

For new homes, a leakage of 6% or less is the threshold to pass. An existing home needs to achieve a leakage rate of 15% or less. In some older homes, however, the ducting system may be largely inaccessible for repair. For these cases, a 60% improvement after failing the initial test may be allowable.

This is an example of a duct tester machine that might be used for commercial buildings. This one is a PANDA 311 Series from TSI.com. It doesn't look all that scary.

To prepare for this test: inspect your ducts ahead of time. Do you see old duct tape? Any mastic used?

For architects or private homeowners doing remodels, where this test may be specified to achieve Title 24 compliance but where no work is actually being performed on the HVAC system as part of the remodel, how do we know it’ll pass and what can we do if it doesn’t?

RL: Have an HVAC contractor come out and inspect it, pre-test it himself. Then the HERS rater can come out and officially test it.

Are there situations where a house will NEVER pass a duct blaster test?

RL: Well, if you’re using the prescriptive method of Title 24 compliance, duct testing is a mandatory measure for additions with over 40 new feet of ducting. However, if the home has asbestos in the system, it’s exempt.

But let’s take another example. Let’s say that this test has been called out, and it’s an existing home, an older home, with an alteration that has triggered a Title 24 compliance report. Let’s say that we need to use the performance method for Title 24, because we’re adding too much glass. We needed the credit from the duct test to get a passing score on the Title 24 report back at submittal time. Now we’re in construction, and it’s time for the actual test. What if it doesn’t pass, even with a 60% improvement on the second try?

My answer would be that you can’t get even a 60% improvement, that means the ductwork is very poor and the homes heating and cooling will be extremely inefficient. The homeowner should consider whether he really wants to keep throwing good money after bad.

What happens during a blower door test?

RL: A home’s air-tightness is measured with a diagnostic tool called a Blower Door. The Blower Door consists of a fan that is temporarily sealed into an exterior doorway coupled with calibrated pressure measurement equipment. The fan blows air out of the house to de-pressurize the home. This negative pressure differential pulls air from outdoors in through any holes, gaps, improperly sealed penetrations in the building envelope, or locations where weatherstripping is loose or missing – to name a few.

Blower Door tests are typically performed at a pressure difference of 50 Pa (0.2 inches of water column) and the findings are measured in Cubic Feet per Minute (CFM). The CF-1R form (the Title 24 report) has the minimum and maximum allowable rates indicated, and the test must show a rate that falls between those figures.

To prepare for this test: Seal off all openings and drains. Close all the windows, put stoppers or plugs in the sinks and tubs, seal off range hoods and chimneys, and plug up any other hole you can find.

So how can you pinpoint where air is coming in? Is there any equivalent to the thermal image test for heat loss?

RL: Not really. But you should look for obvious signs first, like loose weatherstripping. Caulking can help. Thermal imaging won’t help except in some cases where windows may be leaking around the seals or frames. Today’s windows are manufactured with tighter control and they’re better performing with regard to air infiltration. However, window installation may be an issue. Look for cold spots around window openings if using thermal imaging.

Thermal imaging can be an aid in determining where air leakage is causing cold spots. However, you can't always tell what is causing a spot without further investigation. It could be air, moisture, or thermal heat loss.

For thermal imaging to work, you need to do it on a cold day so there’s a visible thermal difference between the interior and exterior temperature. Also, any cold spots you do see may or may not be due to air infiltration.

Why does the air infiltration rate have to fall between two numbers? Isn’t lower always better? Don’t we want to create an airtight home?

RL: A home can actually be too airtight as well as too loose. Some newer homes are so airtight that they can have problems with moisture buildup, which can in turn lead to mold.

I thought mold was mostly a problem in very humid climates, not in California.

RL: If the home is tightly sealed and it also has high-humidity devices such as spas, aquariums, greenhouses, or even if the occupants do a lot of cooking, it can develop serious mold problems, even out here.

What is an Verified Insulation Quality test?

RL: A Quality of Insulation Installation (QII) verification is a visual inspection by a HERS rater to verify optimal quality in insulation installation. The HERS rater verifies the following:

• The insulation is of the proper R-value and type specified in the architectural plans and on the CF-1R Title 24 report
• The insulation coverage does not have any voids or gaps, nor any compression where the insulation is restricted from achieving its full thickness
• All pipes, wires, etc. that are in cavities where the insulation occurs are covered with non-compressed insulation in front and in back
• All electrical boxes are carefully cut out in the insulation in order to provide a tight fit with no gaps or holes

In other words, the QII inspection is looking for the installation to be pretty much letter-perfect, so that the home performs up to what the insulation manufacturer is specifying for their product. The reality is that most insulation is installed by subcontractors who are seeking to finish the job as quickly as possible.

A HERS rater can verify that insulation was properly installed by checking that the right insulation product was used, and that the insulation was applied evenly, without gaps or compression.

This verification is more cumbersome and involved that most other HERS verifications, because the HERS rater might have to make several inspections as different parts of the building are framed. For example, under-floor insulation has to be viewed before the subfloor goes on top, wall insulation should be viewed prior to installing the drywall, and corner cavity insulation has to be viewed from the exterior.

Can you do this test using thermal imaging if the walls are already closed up?

[For the purposes of Title 24 compliance, the QII verification itself has to be visual, with the walls opened up. However, if you are investigating a home's energy performance, thermal imaging can pinpoint problems that would otherwise be invisible.]

Thermal imaging shows missing insulation in this ceiling where it meets the wall - something that you can't see with the naked eye. In this case, what we're seeing is the building's cooling performance on a hot day, and the missing insulation shows up as a "hot" spot.

Where are the most common spots to find insulation gaps?

RL: In addition to the spots described previously – areas around electrical boxes, pipes, wires, and small building cavities – consider these areas as well:

• Behind the tub or shower
• Fireplaces and chimneys
• Skylight window wells
• Exterior edge between building floors
• Interior/exterior wall connections

This last one is important and hard to get to. In places where there’s a connection between an interior and an exterior wall, there will be a three-stud channel that’s typically filled with dead air, and no insulation. A 1.5″ wood stud has an R-value of only 2 or 3, while the mandatory minimum is R13. Insulation is typically installed from the inside, but for these channels, you have to get to them from the outside.

How do you remedy uninsulated spots inside a wall channel?

RL: To remedy the omission of insulation in a wall channel, you have to address it as the carpenters are framing the house. For example, they could cut and install rigid foam insulation. During a QII inspection we’d have to come out and see this part as it occurred.

What is a refrigerant charge test?

RL: The refrigerant charge test is a HERS verification for split-system air conditioning systems, and ensures that the air conditioner has an adequate supply of refrigerant to work with. The amount of refrigerant in the system can dissipate over time through leaks, and if it gets too low, the system’s overall efficiency suffers, possibly even shortening the life of the system. If the refrigerant level is adequate, the system is considered to be fully charged.

There are three ways to verify refrigerant levels.

• A non-intrusive test that analyzes the superheat and the temperature drop across the cooling coils, and compares that information to referenced values. With this information, the refrigerant charge can be calculated. It’s cumbersome to do because of the math, but worthwhile if you depend on your A/C system for comfort.

• A more intrusive method, less frequently used, is to attach a simple pressure gauge to the A/C system to get a direct reading of the refrigerant level within the system. However, this method also requires the HERS rater to obtain a certification from the EPA, because if the refrigerant leaks out, it can damage the environment.

• Within the next few years, manufacturers will begin installing a CID (Charge Indicator Device) with newer models. At this point, a simple reading of that gauge will be all that is necessary to verify the refrigerant charge. However, manufacturers have not provided these devices in most models as of yet.

Refrigerant charge verification is a mandatory prescriptive Title 24 energy calculation compliance in climate zones 2 and 8-15, but when running the performance method of compliance, it can be a selected HERS verification in all climate zones.

To prepare for this test: If you’re doing this test to meet Title 24 compliance requirements, you need to have a HERS rater do it. But, a pre-test can be performed by any HVAC contractor. If you’re not sure the home will pass, you can have an HVAC expert check the system first, and fix anything that needs attention, so that you’ll know the results of the “official” test beforehand. Because of their status as independent inspectors, however, HERS raters are not allowed to fix or change anything themselves. All they can do is run the tests and report the results.

I can see where a refrigerant charge test would be worthwhile for an older A/C system, but what about a brand-new one?

RL: Even with a brand-new A/C system refrigerant charge can be a problem particularly with split systems. In a split system, you have a compressor outside and a suction and pressure line running to an air handler inside. This line can be rather long, and if there isn’t enough refrigerant in the system, it can take enough to fill this tubing that there isn’t enough in the system overall.

OK, say you’re a developer, you want your latest project to be GreenPoint Rated, and to get more points you want to boost the Title 24 performance score on all the homes. To this end, you have opted to include HERS verifications such as the refrigerant charge test in order to gain additional Title 24 compliance credits. How would you go about pre-testing if you had a whole group of tract homes and you need for them all to pass the refrigerant charge test?

RL: In a tract home situation, an HVAC contractor can use sampling during pre-testing. The HERS rater will sample test also, in groups of 7. Bigger builders should realize that HERS raters are an asset that they can use to test and verify different components of construction.

What is a fan watt draw test?

RL: A fan watt draw test is done on air conditioning systems. It’s a simple measure of the energy consumed by the cooling coil fan, and referencing this to acceptable maximum values as shown on the Title 24 report.

What is a verified air flow test?

RL: This test measures the rate of air flow through the ducts. There are several ways to measure, but I am most familiar with the use of an air-flow capture hood, measuring the airflow with all registers open and the filter installed, and comparing the flow rates to be equal to or surpass the duct design criteria of 450cfm/12000 btu (1 ton).

What is an EER verification?

RL: An EER verification matches air-conditioner components for high functional efficiency as a group. This verification applies to split systems, where the air handler, the outdoor compressor, and the cooling coil can all be from different manufacturers. The verification looks up the make and model number for each of these components in a CHEERS online software application that contains data on how efficiently each of these components actually works with the others.

Is the EER verification a pass/fail test? What do you do if it “fails”?

RL: It’s pass or fail. What we do is match up the components for high EER compatibility. Either the proposed system makes it or it doesn’t. For example, suppose you have a system design that calls for a Carrier compressor, a Train air handler, and a third-party cooling coil. We do an EER lookup and it turns out that the off-market cooling coil was lousy pick.

At this point, you can remedy it in one of these ways:

• Call the contractor and tell him that the components don’t match, and give him some other options that do match.
• Re-calculate Title 24 report and pick another HERS measure based on what the project will best support.

How far off can they be in terms of efficiency if they’re not well-matched?

RL: I’m going to go out on a limb and give you a rough estimate, and say that mismatched components in a split system could degrade overall system efficiency by as much as 10-15%.

Is the EER verification something that you’d have to think about way ahead of time, during project design?

RL: Yes, this is something that should be considered early on. The architect or the mechanical systems designer should contact a HERS rater prior to specifying these components. It can stop you from making a bad purchase. Then, when you add this as a verification for Title 24 compliance credit, you can be confident that your system components can perform together as well as expected.

What is the maximum cooling capacity test?

[Usually recommended for commercial buildings. We're going to punt on describing it here, because it's rather complicated.]

What is the supply duct surface area reduction test?

RL: This is a verification measuring the efficiency of the duct design, again mostly done on large commercial buildings with very extensive HVAC systems. The HERS rater physically measures the duct system as installed and checks this measurement against the calculated allowable area of duct surface from the Title 24 report, and verifies that the existing duct systems meets this allowable criteria.

What are the visual field inspections that apply to duct systems?

RL: There are several inspections related to where the ducts are located and how well they’re insulated. All of these inspections are credits towards achieving a higher Title 24 performance score. The two buried-duct inspections only apply to ducts that are located in the attic.

• Buried ducts: The HERS rater verifies that the attic supply ducts are buried under the required R-value insulation, and that the ducts make contact with the ceiling sheet rock. Signs must be visible that say “caution, buried ducts” [so that anyone doing subsequent work on the home doesn't inadvertently damage them]
• Deeply buried ducts: In addition to the buried duct requirements as described above, the HERS rater verifies that the attic supply ducts have an additional R-25 insulation over them if fiberglass insulation is used, or R-31 for cellulose insulation.
• Ducts in conditioned space: This test applies only to projects where the ducts are located in conditioned space, rather than in the attic or a crawlspace. The HERS rater does a visual inspection to verify that 100% of all supply ducts are within the conditioned space envelope.

[Radiant barriers, which can earn compliance credits in Title 24, are verified by a building inspector, not a HERS rater.]

Under what conditions would any of these tests NOT be advisable?

RL: The climate zone for each project needs to be considered to get the best bang for the buck. In other words, tests that focus on air conditioning may not be advisable in climate zones where there is little demand for cooling.

[They don't buy you as much on the Title 24 score, either. For example adding a radiant barrier in San Francisco does nothing to improve a home's Title 24 performance score, but adding one in Livermore or Los Angeles certainly does. ]

What happens if a project fails a HERS verification?

RL: The HERS rater has to submit the results to the HERS registry as a failure.  The necessary repairs should be done by the contractor, and then the HERS rater is called back to perform the test again.

When does each of these tests occur in the project cycle?

RL: Various stages. The important issue is usually to observe a complete and finished component for verification, prior to its being hidden by subsequent construction. One example is the verification of quality of insulation installation (the QII test), which may require several trips. Duct verifications are best done after all or most of the construction activity is completed, and there is no possibility of workers subjecting delicate items such as ducting to damage.

How much do these HERS tests cost?

RL: Well it depends in part on the size of the building and how cumbersome the test is to perform. A duct blaster test might start at $250-$300, because it can be done in one trip and it only takes a couple of hours. Some duct blaster tests are more challenging than others. A QII insulation test, which requires several inspections over a few weeks’ time, could be more.

How can the architect, owner, and builder ensure that the project will pass on the first try?

RL: Perform your own pre-inspections and employ expert help prior to the test date to prepare the components for testing. For example, good HVAC contractors will often test their own work anyway, although many don’t care enough about quality to do this. But, they should.

Compare it to smogging your car. Emissions is a state test, and it’s pass or fail. You can go to a mechanic ahead of time for pre-smog testing to find out if you’ll pass, and get any needed repairs done prior to having the official smog check.

"Will this cardboard box pass Title 24?"

What do architects need to know about working with local building departments?

RL: Their compliance review starts with the CF-1R form, which is the Title 24 compliance report. But most people don’t know how to read a CF-1R report. Even architects, building officials, and plan checkers don’t always know every aspect of compliance.

Building departments can’t interfere with HERS verifications, which is a State-level program. However, with the increasing levels of reporting and inspection, it will be harder to do last-minute equipment substitutions.

[One thing to note is that Title 24 reporting relies on specific stated performance criteria for products ranging from windows to water heaters, and any substituted product needs to have an equivalent or better efficiency rating. This means that the person responsible for selecting equipment and products must be fully aware of any assumptions that were used when preparing the Title 24 report for the project.]

Any famous last words?

RL: Here’s one thing you should know: All three of the official HERS providers are mandated to do follow-up inspections to check up on their own HERS raters. So, the homeowner could get a call or a letter notifying them that this is happening. Usually they’re OK with it, it gives them reassurance that the system is really working as intended.