R Value Of 3 Spray Foam Insulation

Open cell foam insulation values r3 r4.

R value of 3 spray foam 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 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. 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. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.

All these have r values ranging from r 3 2 to r 3 8 per inch. For example if a 2 4 wall has 3 in. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. For 6 inches r 15 or r 19 etc.

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. 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. Closed cell spray foam r values. Of closed cell foam insulation the r value of the studs is based on a stud depth of 3 in not 3 1 2 in.

It s made of environmentally sound closed cell polyisocyanurate foam bonded to a durable white matte non glare aluminum facer and a reflective reinforced aluminum facer. As a benchmark one inch of solid wood has an r value of 1. 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. For example closed cell spray foam depending on brand can offer an r 6 or r 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. Along with knowing the r value of a particular insulation it is also important to calculate the r value of a total system. For example if a 2 4 wall has 3 in. When stud bays are partially filled with closed cell spray foam the exposed portion of the studs reduces their r value in comparison to a wall that is totally filled with open cell spray foam.

Why spray foam insulation is so effective in meeting code requirements is that it has a higher r value per inch of product used than batts. 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. Of closed cell foam insulation the r value of the studs is based on a stud depth of 3 in not 3 1 2 in. Closed cell spray foam insulation.