Spray Foam Insulation R Value

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.

Spray foam insulation r value.

Focusing on spray foam insulation materials there is a difference between the two main types. 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. For example closed cell spray foam depending on brand can offer an r 6 or r 7 per inch. Open cell foam insulation values r3 r4.

If you want to install spray foam in a stud wall and price is no object then it would seem to make sense to specify closed cell spray foam right. 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. Closed cell spray foam r values. I m not going to dive into the energy code here but these numbers apply to many climate zones the latter being allowed under the ua tradeoffs rule.

However there are open cell spray foam insulation products actually offer r 3 7 per inch such as icynene classic and. For 6 inches r 15 or r 19 etc. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. 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.

Since closed cell foam has a higher r value per inch installers generally spray 2 in walls and 3 in rooflines to meet the energy code requirements of r 13 and r 19 respectively. Bulky materials resist conductive and to a lesser degree convective heat flow in a building cavity. 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. Rigid foam boards trap air or another gas to resist conductive heat flow.

Open cell spray foam has an r value of about r 3 7 per inch while closed cell spray foam has an r value that may be as high as r 6 5 per inch. Traditional insulation such as cellulose or fiberglass is not comparable to spray foam insulation in r value as those insulation methods use r value of heat transfer. According to industry publication fine home building the r value for open cell spray foam is between r 3 5 r 3 6 per inch. 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.

It has a lower r value per inch than closed cell foam and is vapor permeable.