How do I insulate the attic stairs to R-38?
According to 2015 IRC Section N1102.2.4:
“Access doors from conditioned spaces to unconditioned spaces such as attics and crawl spaces shall be weatherstripped and insulated to a level equivalent to the insulation on the surrounding surfaces.”
Our Habitat for Humanity affiliate insulates the attic to R-38 with blow insulation, so we are trying to figure out how to insulate the attic stairs to the same value. Currently, we build a box that we fit the stairs into, place a lid on top, and attach two pieces of 1/2″ XPS to the lid to make an R-5 attic hatch. I have looked into products such as the Battic Door and Energy Guardian’s products, but we would like to use rigid foam if possible, since we receive it as a donated product.
Would it be possible to use four layers of 2″ XPS to achieve R-40? If so, how would you attach that to the lid?
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