Roof Insulation Thickness R Value

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Roof insulation thickness r value.

R value chart for enerfoil tm rigid foam faced insulation. Thickness inches r value in i p imperial rsi r value in metric 0 5. All these have r values ranging from r 3 2 to r 3 8 per inch. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13.

Closed cell spray foam has a far better r value per inch than other less effective insulations like cellulose fiberglass or even open cell foam. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. Closed cell spray foam insulation. Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value.

Recommended insulation levels for retrofitting existing wood framed buildings. R value measures how well certain building insulation materials can resist heat. Existing 3 4 inches of insulation. Add insulation to attic.

See the department of energy s doe ranges for recommended levels of insulation below. When determining how much insulation you need don t guesstimate calculate.