Crawl space questions
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| Posted in Energy Efficiency and Durability on
You answered a question on moisture in the crawl space for my sister’s old house . Now I have two more questions.
1. Since her house is so large and they mainly only use certain rooms, is it possible to only air seal a section of it? And I know it must be for air movement that you put the plastic on the ground; could I put it closer to the floor joists?
2. When running the plastic in the crawl space – what do you use to join pieces together and how do you seal it around the concrete piers and other structures under the house?
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Replies
William,
Q. "Since her house is so large and they mainly only use certain rooms, is it possible to only air seal a section of it?"
A. It only makes sense to air seal only a portion of the house if the rest of the house is thermally isolated from the conditioned space, and if you are only heating or cooling the portion of the house that has been air sealed. That also means that any doors between the conditioned and unconditioned space need to be exterior doors with weatherstripping, and any partitions between the conditioned and unconditioned space need to be insulated.
Q. "I know it must be for air movement that you put the plastic on the ground; could I put it closer to the floor joists?"
A. The plastic on the dirt floor of a crawl space is not installed to limit air movement. It is installed to limit the evaporation of moisture contained in the soil. It should be installed in direct contact with the soil.
Q. "When running the plastic in the crawl space - what do you use to join pieces together and how do you seal it around the concrete piers and other structures under the house?"
A. Either housewrap tape, European specialty tapes, or duct mastic. For more information on this question, see:
Air-Sealing Tapes and Gaskets
Building an Unvented Crawl Space