Spray Foam Insulation R Values

R values are additive so you can multiple the number of inches of insulation thickness times the r value to arrive at a total insulation value.

Spray foam insulation r values.

The r value of spray foam insulation is approximately 6 per inch so those using spray foam as their insulator will need about 6 3 inches of thickness to reach r 38. The r value of closed cell foam is r 6 5 7 per inch. Open cell spray foams are between 5 and 1 lbs per cubic foot and have an r value of 3 0 4 0 per inch of insulation. Insulation r value measures how well a particular insulation resists heat flow.

Bulky materials resist conductive and to a lesser degree convective heat flow in a building cavity. 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. The r value of fiberglass insulation is approximately 2 2 per inch so much thicker fiberglass insulation is required to achieve the same r value of 38. Insulation materials run the gamut from bulky fiber materials such as fiberglass rock and slag wool cellulose and natural fibers to rigid foam boards to sleek foils.

Open cell spray foam insulation is air impermeable and is applied with a minimum of 3 5 on average and can be used for attics interior floors walls and soundproofing. Spray foam the truth about r values r value does not measure heat movement carried in the air. It performs much better than any form of batt for stopping air flow but it is not as complete of an air seal as closed cell spray foam. Open cell spray foam typically has an r value of 3 5 per inch and it should be noted that open cell does not form a tight air seal.

Contractors often use it to insulate under slabs ceilings walls and roofs. All these have r values ranging from r 3 2 to r 3 8 per inch. Rigid foam boards trap air or another gas to resist conductive heat flow. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.