Roof Insulation Thickness R Value

The higher the r value the greater the insulation performance.

Roof insulation thickness r value.

Add insulation to attic. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. R value measures how well certain building insulation materials can resist heat. When determining how much insulation you need don t guesstimate calculate.

Measuring the r value of polyiso roof insulation at the website of pima polyisocyanurate insulation manufacturers association discusses long term thermal resistance lttr the astm standards underlying the r values for polyisocyanurate insulation and provides r values for various thicknesses of polyiso which increases in r value per inch as total thickness of the installation increases. Thickness inches r value in i p imperial rsi r value in metric 0 5. 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. 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.

Know exactly how much you need with our project calculators. Existing 3 4 inches of insulation. Closed cell spray foam insulation. R value chart for enerfoil tm rigid foam faced insulation.

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. Conditioned per atsm c1289 test method astm c5181 2.