What is R-Value?
R-Value is a measurement of an insulation material’s thermal resistance.
Thermal resistance is…wait for it…the ability to resist heat transfer or loss through conduction. Basically, if a warm or hot material comes in contact with a cold material, the heat is transferred to the cooler surface. This means the insulation material’s ability to resist heat transfer through conduction – its thermal resistance. Fiberglass and cellulose only work to prevent conduction, while spray foam works to stop conduction and convection, or air movement.
Now, to get into what you came here for – spray foam insulation R-Value.
Spray Foam Insulation R-Value
The R-Value for spray foam insulation can vary depending on the product, manufacturer, and other variables.
Open cell spray foam insulation is R-3.6 to R-3.9 per inch. This R-Value is normal for open cell spray foam.
Closed cell spray foam insulation is R-6 to R-7 per inch.
Not all spray foams are created equal, which is why you’re likely wondering why there is a difference in the per inch R-Value of open cell and closed cell spray foam. There are a couple of things that affect the R-Value of spray foam – the type of foam, the age of the foam, and how well it is resistant to moisture.
The type of foam insulation affects the R-Value just in how they are made up. Open cell is a lighter material, so the R-Value is lower, while closed cell is thicker and denser so the R-Value is higher. This is because it takes longer for heat to transfer through the closed cell spray foam due to its denser composition.
Spray Foam Insulation for Your Home
Spray foam and the air seal it creates is what makes it a premium insulation material, not the numbers.
The air seal created by foam insulation keeps air from moving freely into and out of the house. It works to help maintain a constant temperature, which in turn helps your air conditioner and furnace not run constantly.