Roof Insulation Thickness R Value

Closed cell spray foam insulation.

Roof insulation thickness r value.

See the department of energy s doe ranges for recommended levels of insulation below. Existing 3 4 inches of insulation. Know exactly how much you need with our project calculators. The higher the r value the greater the insulation performance.

When determining how much insulation you need don t guesstimate calculate. Recommended insulation levels for retrofitting existing wood framed buildings. 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.

Add insulation to attic. 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. Conditioned per atsm c1289 test method astm c5181 2. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13.

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. 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.