Quote:
Originally Posted by williecoyote
The current school of thought (which goes against everything I was taught) is to
seal all vents, foam any holes which penetrate the floor, put plastic on the ground and up the foundation walls, and install a crawl space dehumidifier with the drain line run away from the foundation.
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With today's push for ever tighter and more efficient homes, sealing the crawlspace is definitely advocated by building scientists. A sealed vapor barrier on the floor and insulated foundation wall and rim joist are part of the non-vented crawlspace mantra. In addition, you must ensure the exterior of the house is designed to shed water away from the foundation.
I recently read an article about duct sealing in crawlspaces. I cannot recall where I read the article, but the author recommended sealing the joints with mastic and then covering the ductwork with insulation fastened with staples. He stated there are no sealing tapes suitable for long-term performance/durability in the crawlspace. Of course, if you seal the crawlspace and allow the humidity to approach the conditioned space, I don't see why tapes cannot perform adequately.
If your ductwork is flex, then you definitely have humidity problems or serious leaks to cause condensation.