Duct, air handler, condensation line sweating in crawl space

Billi Zhu

4 years ago

Home inspector noticed water puddles in crawl space due to Duct, air handler, condensation line sweating. What needs to be done to fix it? Does the crawl space needs to be seal? or the hvac system needs to be replaced?

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Comments (3)

PRO
Charles Ross Homes
4 years ago
Condensation occurs when humid outside air contacts a surface which is at or below the dewpoint temperature. It's pretty common in conventional (vented) crawl spaces in my (coastal VA) area during the summer months. It can produce mold/mildew growth.

You can seal and insulate the piping and ductwork to mitigate the problem, but it's pretty hard to make the insulation air tight, which you'd need to do to prevent condensation. Another, better, option is to convert the crawl space from a vented to a "conditioned" crawl space. You can find out how to do that by clicking on the link below:

https://www.nrel.gov/docs/fy13osti/54859.pdf
sktn77a
4 years ago
last modified: 4 years ago
Unfortunately, "conditioning" a crawlspace to eliminate this issue costs an arm and a leg ($20,000 plus). You need to make sure the entire floor of the crawlspace is covered with plastic sheet and that the seams in the sheeting is taped (you have lots of gaps in yours). This will cut down on the humidity in the crawlspace and reduce (but not eliminate) the problem.
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PRO
Charles Ross Homes
4 years ago
Our company has been constructing homes on conditioned crawl spaces since 1999. We find the cost to construct a conditioned crawl space in new construction is comparable to the cost of a conventional, vented crawl. This is because the area of crawl space walls to be insulated is typically less than the floor area to be insulated and the required R-value for crawl space walls is less than for a floor. The expensive component is the spray foam insulation used for sealing the rim joist.

The cost to convert a conventional vented crawl space to a conditioned crawl space in our area runs $8K to $10K +/- for a home with a 2,200 SF footprint and 2 ft high masonry walls provided a reputable company does the work. There are plenty of companies which charge a whole lot more for the same job. You can run up the cost if you choose a heavy duty reinforced vinyl soil vapor barrier in lieu of polyethylene sheet and if you purchase the industrial duty dehumidifier that is rarely, if ever needed in a conditioned crawl space, but gets pushed hard by sales people.