Title 24 Compliance for Alterations and Remodels

Title 24 Compliance for Alterations and Remodels

Posted on 30. Aug, 2010 by in Designing for Compliance, Heating and Cooling, Project Management, Windows and Glass

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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.

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.

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About the author
 Rebecca Firestone has been working in the Bay Area since 1998 as a technical writer, business content developer, architectural filing lady, marketing director, and sorcerer’s apprentice.


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