The North Carolina Energy Efficiency Alliance has recently completed a study to identify commonly missed requirements of the North Carolina energy code, and they have followed that up with some training materials to help builders improve their homes. The training materials are available online at the NCEEA web site. What did they find?
75% High-efficacy light bulbs: This have been a requirement of the code since 2012, but only 46% of the homes they checked got it right. Based on our company’s experience, I’m surprised it was that many, although things have been improving recently. This is particularly disappointing for a whole lot of reasons:
- It just doesn’t get any easier. It’s light bulbs!
- The payback is under a year.
- These light bulbs last much longer AND pose substantially less risk of fire.
- The energy savings from using these bulbs in all of your fixtures could be as much as 5% of your whole-house energy bills.
Both LED and fluorescent light bulbs meet this requirement. These bulbs use about one-quarter of the energy of a standard incandescent bulb, and about one-third of the energy of a halogen bulb. The biggest thing that builders (and code officials) are doing wrong is just not paying attention to make sure these bulbs get installed. In some cases, fixtures like ceiling fans or the trendy “Edison” fixtures come with incandescent bulbs in them and they don’t get changed. The Edison bulbs are particularly egregious (and pointless) since they can use up to twice as much energy as a typical incandescent bulb, with an even shorter life span. Do yourself a favor and change these out immediately with a LED Edison-look bulb. The cost is about the same.
Ducts not sealed very well: Their team found that sealant was used on the ducts in all the homes they checked, but that it wasn’t applied properly. This can impact the longevity of the duct sealing job as well – a system that tested to meet code initially may fall apart at a faster rate than expected.
In our work, the biggest problem we see with ducts is actually a “loophole” in the code. The code requires ducts to be tested for leakage, but it doesn’t specify whether the test is to be done at rough-in or when the house is completed. If the test is done at rough-in, the metal duct boots are sealed for the test and you get no leakage at that location. If you test the same house after drywall, you can often get a lot more leakage if the boots are not sealed to the subfloor or the drywall. For homes that have ducts located in unconditioned attics and crawlspaces, this can add up to a lot of leakage – both for the ducts AND for the home’s overall airtightness. So, when the test is done at rough-in someone should follow up to make sure that the boots get sealed to drywall before the home is completed.
Thermal envelope sealing: Backing on kneewalls was found to be done poorly and in a non-airtight way. The sealing of dropped soffits was also found to be lacking.
In our experience, this is also partially attributable to a “loophole” in the code. The energy code requires that airtightness be tested at less than 5 ACH50 with a blower door OR the builder can sign a certificate that says they visually verified a checklist of air sealing items. Unfortunately, that checklist isn’t on the form that the builder signs, and most builders aren’t going to go back to reference the full text of the code before they sign it. Builders who participate in above-code programs like Energy Star, Greenbuilt NC, or Duke Energy Progress’s incentive program get blower door tests – so if their kneewall backing or other air sealing details are leaky they find out. The blower door doesn’t lie, and it’s a great demonstration of where a home is leaking. Builders who don’t get blower door tests may not realize that their backer materials aren’t installed in an airtight way. Code officials are typically checking to make sure that appropriate materials are being used, but without experience with a blower door they might not know what to look for in a good installation. And giving builders qualitative feedback on installation isn’t usually what code inspection is really about anyway.
Insulation installed poorly: Speaking of getting feedback on installation… another finding was that insulation wasn’t installed well. And when insulation isn’t installed well, it doesn’t work properly. Builders and code officials are used to looking to see that insulation is present and that it’s labeled with the proper R-value, but that’s about it. There’s a lot more to it, as those builders of high-performance “program” homes know. Any insulation can be installed poorly and suffer for it but in our experience fiberglass batts are the toughest to get right. What are some things that go wrong?
- Insulation should fill the entire cavity, and cover the whole exterior of the building with no missing places.
- Insulation should not be compressed: fluff it out to fill its entire intended thickness. Everywhere!
- Cut around outlets, split around wires, don’t allow other “stuff” in the building cavity to compress it.
- For non-foam insulation, encapsulate the insulation with a six-sided rigid surface that is completely air sealed.
- For spray foam insulation, make sure the proper thickness is achieved, and be careful to prevent low spots or peel-back.
- When trades come in to work on plumbing or wiring, replace or fix insulation that they may have damaged. This might include insulation pulled down from a floor above a basement or crawlspace, removed from a section of wall, or trampled in an attic. Since these trades may not be as experienced in proper installation techniques, the general contractor needs to be extra careful that the insulation is restored to its full function.
The NCEEA has some great installation videos to help builders be successful with these strategies and more. Be sure to check them out!
Copyright 2016 Amy Musser.