R- Value and Spray Foam Insulation

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What is R-Value?

R-value is the measure of insulation ability to transfer heat and air flow. The thicker or amount of insulation you have raises your r-value. Traditional R-value test will measure only one component of the heat transfer process which is called the Conduction (the transfer of heat by direct contact). R-value alone does not properly reflect the insulating power of spray foam insulation.

The effectiveness of an insulation material’s resistance to heat flow also depends on how and where the insulation is installed.  Insulation that is compressed will not provide its full rated R-value. The overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself because heat flows more readily through studs, joists, and other building materials. Spray foam insulation is labeled has air impermeable insulation and does not have the R-values as traditional insulation.  Insulation that fills building cavities densely enough to reduce airflow can also reduce convective heat loss.

Spray Foam and R-Value

Spray foam creates a thermal barrier to heat because it is not easily transferred through the foam. To consider r-value for foam you have to consider your regions and requirements for air impermeable insulation. 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. 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. The R-value for open cell is typically around 3.7 at 1″ thick and varies by manufacture. Closed cell spray foam insulation is vapor and air impermeable and is applied with a minimum of 2″ on average, with use on on interior and exterior building applications. The R-value for closed cell is typically around 6.7 at 1″ thick and varies by manufacturer. Note that some commercial and industrial buildings may require higher R-Values – always check with local building code inspectors.

Refer to the Region Map below to find your region and the required minimum R-values for spray foam insulation where you live.

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