As Steve Easley writes in his recent BUILDER article Air-Sealing Whys and Hows, the new energy code mandates blower-door verification for homes, with a maximum 3 ACH50 in climate zones 3 to 8. If you fail the test, you’ll have to call your crews back in to air-seal as a retrofit. Three ACH50 is a tough mark for some builders to get to from the previous requirement of 7 ACH50. But there are good reasons for builders to focus on airtightness.
“As much as a third of a home’s heating and cooling bills can be traced to air infiltration and exfiltration. So tightening up a house is an important step in energy efficiency. But that’s not the only reason airtightness matters. In addition, air leaks bring warm, humid air into contact with cold surfaces. That creates conditions ripe for mold growth and decay. And of course, drafts in homes are a comfort issue that can lead to homeowner complaints. Some people mistakenly believe that air leaks help walls dry out, but it’s the opposite, as the leaking air is almost always warmer and wetter than the air it’s driven to. In my experience, the biggest cause of water-related damage in buildings is from water leaks from the outside, and the second is damage due to air leakage. Tighter is better as far as managing moisture to prevent rot and decay.”
Air leaks in the building shell can be costly and difficult to fix after the fact. But air-sealing a new home under construction should only take a few hours. In the article, Easley takes a close look at simple approaches that you can use to help you hit 3 ACH50 the first time out. Read more.