Roof Insulation Thickness R Value

R value chart for enerfoil tm rigid foam faced insulation.

Roof insulation thickness 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. Add insulation to attic. See the department of energy s doe ranges for recommended levels of insulation below. Existing 3 4 inches of insulation.

Thickness inches r value in i p imperial rsi r value in metric 0 5. The higher the r value the greater the insulation performance. R value measures how well certain building insulation materials can resist heat. Conditioned per atsm c1289 test method astm c5181 2.

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

All these have r values ranging from r 3 2 to r 3 8 per inch. Closed cell spray foam insulation.