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Common spray foam application questions

Depending on the application or area of the home being insulated, there are some common spray foam application questions we’ve answered here. From thermal barriers to vapor barriers, get the answers you need.

Have a specific question? Contact the Icynene Engineering team at 1-800-758-7325 or email

Do I need a thermal barrier?

In an occupied space, you need a thermal barrier adjacent to either low-density or medium-density foam. This could be ½-inch gypsum board, or a code-prescribed barrier per R316.4. See the ESR of each Icynene spray foam product to determine the intumescent coating thicknesses that could be used to create a thermal barrier directly on the spray foam.If the space is unoccupied, you don't need a thermal barrier.

Do I need an ignition barrier?

In unoccupied attics and crawl spaces with limited access and not used for storage, the code allows for an ignition barrier, instead of a thermal barrier, to be applied adjacent to or to coat the spray foam. But most of Icynene’s low-density or medium-density foam products do not need a prescriptive ignition barrier or an intumescent coating in such situations.See the ESR for the Icynene spray foam product to determine exact requirements for ignition barrier situations.

Do I need a vapor barrier?

This depends on your local code requirements; it’s affected by climate and the elements in the building envelope.

What R-value* do I need?

This depends on your local building thermal envelope code requirements. ICC code allows Icynene spray foam insulation to be installed with less than the prescriptive minimum R-value* and still meet the intent of the code. Compliance based on simulated energy performance requires that a proposed residence (proposed design) be shown to have an annual energy cost that is less than or equal to the annual energy cost of the standard reference design that is based on the minimum prescriptive standard. When the air tightness of the building envelope is factored into the computer calculations, the building will require less R-value* than the prescriptive level mandates. Typically the R-value* can be reduced by 20-25%, depending on the code version that is being used. Icynene may be able to help with REM/design analysis.

See:2009, 2012, 2015 IECC Section 405 – Simulated Performance Alternative

R means resistance to heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before you buy. There are other factors to consider. The amount of insulation you need depends mainly on the climate you live in. Also, your fuel savings from insulation will depend upon the climate, the type and size of your house, the amount of insulation already in your house, and your fuel use patterns and family size. If you buy too much insulation, it will cost you more than what you'll save on fuel. To get the marked R-value, it is essential that this insulation be installed properly.