I live in St. Pete, FL, and want to know more about closed-cell foam insulation for my crawlspace. Is it safe to use?

Question

I live in St. Pete, FL, and want to know more about closed-cell foam insulation for my crawlspace. Is it safe to use?

Asked by David Deering

The house is hot and moist during summer, freezing in winter, and I believe most of it is due to the crawlspace. House was built in the '50s.

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Answers

Polly Osborne, FAIA, LEED AP's picture

Even in dry climates, you'd be amazed how much moisture comes through the floor.

I think closed cell insulation might be ok, but when I think about using it I always ask the question: is moisture going to get trapped by it?Human habitat has moisture that could get trapped in, and possibly harm, the floor joists, but I hope someone else will weigh in on this, too.

My first thought, and it is cheaper than home foam insulation, is to:

  • lay a vapor barrier in the crawlspace,
  • run it up the foundation walls and seal it,
  • then add positive ventilation in the crawlspace with a small fan built for this purpose,
  • then insulate the floor with any insulation that is designed to fit between joists, such as cotton batts or formaldehyde-freefiberglass, or cellulose in a netted installation.

For more information:

Read Florian Speier's Q&A "We have an unheated crawlspace under our house that we would like to insulate."

Also, read Danny Kelly's Q&A "What kind of waterproofing can you use in crawlspaces to help with going green?"