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Tags: audit, improvement, infiltration, insulation, report, target
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Comment by David Willson on May 2, 2011 at 12:40pm Tim,
I didn't do a zone pressure test on the attic or the crawlspace with respect to the interior because both are well vented to the outside. My personal approach is to always air seal the crawlspace from the bottom as thoroughly as possible. The government research report that said 60% (!) of indoor air with windows closed in the winter comes from the crawlspace has affected my thinking. I used to think the ceiling was the most important but now I think the subfloor is, though the ceiling is a close second. So I air seal both while monitoring the blower door and not going tighter than 70% of 0.35ACHnatural. Most clients, when I say I need to recommend that they add mechanical ventilation if the infiltration is between 70% and 100% of ACHn, say they'd rather open a window if they feel it's too stuffy and skip the additional cost. Below 70%, we're required to provide mechanical ventilation and that's often a deal breaker for the client so 70% is usually my air sealing limit.
Comment by David Willson on May 2, 2011 at 11:43am William, thanks for the suggestion. Here's what I'm looking at right now.
I'm meeting with a spray foam company at the site soon. He says he can spray 2 inches of closed cell on the bottom of the subfloor with only the standard 18" of clearance. Sounds iffy to me but he says he can do it. If so, that'll take care of both infiltration and insulation issues in subfloor. I'd love to fully seal the crawlspace; I've done enough of them now to believe in it but this one's tough: completely below the outside soil so considerable ditching and a sump or two will be in order or there's no use putting a barrier on the ground because the water will still seep through and sit on top of the barrier. I use Americover's 12mil barrier and weld the seams but rising water will still seep through the seams somewhere.
Comment by Tim Swinkels on April 28, 2011 at 7:46am Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy, under the American Recovery and Reinvestment Act) and brought to you in partnership with Home Energy magazine.
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