What are typical crawspace air leakage vectors?
Alan B| Posted inEnergy Efficiency and Durabilityon
I’ve done a little bit of searching and not come up with much except that its a common phenomenon, i have a very old probably more then a century balloon framed house with a 70/30 basement/crawlspace, and the blower door showed a lot of air coming from the crawlspace, and i’ve gone in there (a messy and claustrophobic endeavor) but did not find any obvious places air was leaking into the house from.
Its uninsulated, uncovered dirt built with a brick foundation and has ductwork, natural gas piping, and water/drainage lines running through it, all coming from the basement so they are not the leakage vectors.
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Replies
Alan,
First of all, outdoor air can be pulled into a crawl space or basement through the soil. So the very first step is to cover the dirt floor in your crawl space with a durable layer of polyethylene without any holes in it. The poly should be installed in an airtight manner; seams should be sealed, as should the perimeter, using high-quality tape or Tremco acoustical sealant.
After that work is done, the next candidates for air sealing are the rim joist area (especially the crack between the sill and the top of the masonry wall), any penetrations, and windows (if any).
For more information, see these resources:
Building an Unvented Crawl Space
Air-Sealing a Basement