Were should you not use spray foam?

Are you looking to install spray foam but aren't sure where you should or shouldn't be spraying it?


Trevor Van Keulen


Avoid spraying foam near anything that gets hot. Heating appliances, furnaces, hot water heaters, and canned lights are good things to avoid. A good way to safely insulate the area around places that get warm is to install a fire barrier between the insulation and the appliances. By finishing a space with drywall or gypsum board you have created a safe barrier to cover the insulation.


Depending on the climate you live in, the underside of the roof may not be a good choice. By spraying on the underside of a roof you create a WARM roof. This means that the heat absorbed by the shingles, which would normally be radiated into the attic space below, is now trapped in the shingles. In higher climate zones it is much less of an issue due to lower solar intensity, but some companies will void the warranty on a roof all the same. We recommend installing a ceiling in whatever space is being insulated and installing insulation from above.


Spray foam expands quickly and gives little time to react to the forces that it can apply to surrounding surfaces. Spraying on a flat surface gives plenty of room for the insulation to expand and cure, but small cavities filled with insulation can cause damage to drywall or leave voids that do not have any insulation. When spraying extremely small, enclosed spaces it is difficult for even an expert to determine what kind of coverage you will have or the damage the expansion could cause.

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