Spray Foam Insulation R Values

Insulation r value measures how well a particular insulation resists heat flow.

Spray foam insulation r values.

These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3. 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. When the time comes to assess the type of insulation your home needs r value is a common term you will hear.

Spray foam the truth about r values r value does not measure heat movement carried in the air. The r value for open cell is typically around 3 7 at 1 thick and varies by manufacture. 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. 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.

Contractors often use it to insulate under slabs ceilings walls and roofs. 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. 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. All these have r values ranging from r 3 2 to r 3 8 per inch.

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. 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. Rigid foam boards trap air or another gas to resist conductive heat flow. The r value of closed cell foam is r 6 5 7 per inch.