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Building Homes or Extensions/Ridged foam Insulation

Expert: Dave Johnson - 10/12/2008

Question
I have sheets of Dense ridged foam insulation,That was removed from Large commercial Freezer. that is 5-1/2 Thick that is 9'long about 18" wide I want to install it under my house Crawl space between floor Joist and in the attic, how much air space do I need to leave Between foam and Floor/Decking?

Answer
Hi Paul,
Actually, you need to leave little or no space.
Ideally the way to apply this is to cut as closely as you can, and then use a canned spray foam insulation to seal up any little gaps.
You will surely find a difference in your fuel use!!

Best of luck,

Dave

Questioner's Rating

Rating(1-10)	Knowledgeability = 10	Clarity of Response = 10	Politeness = 10
Comment	This is what I Thought But A friend of mine said there has to be an air space so I asked the expert.I noticed when spray foam that expands they apply it right to the wood and it expands with no air space.