Roof Insulation Thickness R Value

Conditioned per atsm c1289 test method astm c5181 2.

Roof insulation thickness r value.

When determining how much insulation you need don t guesstimate calculate. Existing 3 4 inches of insulation. Closed cell spray foam insulation. 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.

Add insulation to attic. All these have r values ranging from r 3 2 to r 3 8 per inch. R value measures how well certain building insulation materials can resist heat. 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.

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. See the department of energy s doe ranges for recommended levels of insulation below. The higher the r value the greater the insulation performance.

Know exactly how much you need with our project calculators. Recommended insulation levels for retrofitting existing wood framed buildings.