Foam R Value

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.

Foam r value.

I ve written several posts about how to insulation basement walls in which i promote the use of foam board insulation as the first line of defense against moisture and mold. Insulation level are specified by r value. Closed cell 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 in your attic to reach r 30 if you live in zones 2 or 3.

Recommended home insulation r values. A typical 2 4 stud filled with open cell spray foam will have an r value between 10 5 and 14. During the late 1970s the ftc federal trade commission went after urethane foam. For example a wall with 3 fiberglass batting r value of 10 8 11 9 may have an overall r value of nearly 14 because of siding sheathing and drywall.

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. For example closed cell spray foam depending on brand can offer an r 6 or r 7 per inch. R value is a measure of insulation s ability to resist heat traveling through it. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.

Because of this i often get questions about which type of foam board insulation to use and what r values these products provide. Also called styrofoam insulation this is the least expensive material. It provides r values that range from 3 6 to 4 2 per inch. There are three basic foam insulation board products on the.

The higher the r value the better the thermal performance of the insulation. Spray in place polyurethane is an absolute minimum of three to ten times as effective as any other insulation available today. The r value is r 3 5 to r 3 6 per inch so filling a 2 4 cavity yields about an r 13. Nor can you use the r value of a foam insulation if it is in sheet form and compare it to the r value of spray in place foam insulation.

Each type comes with unique advantages. Along with knowing the r value of a particular insulation it is also important to calculate the r value of a total system. All these have r values ranging from r 3 2 to r 3 8 per inch. Closed cell spray foam r values.

Products with a higher r value have a higher cost but have an increased capacity to resist heat flow and therefore provide greater insulation. 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.