Although building codes are often hard to read and subject to interpretation, in most cases they require that a thermal barrier be used to protect spray foam insulation. Exposed spray foam insulation can be a hazard, since it may ignite if exposed to excessive heat. A thermal barrier, which is usually drywall, protects spray foam from exposure to heat, reducing the risk of ignition.
Thermal Barrier Requirements
When spray foam is used in a residential building, the International Residential Code (Section R316.4) requires that it be separated from the living quarters by 1/2-inch drywall or a similar approved material. Note that this does not apply when spray foam is used as a roofing material, when it is covered by at least 1 inch of concrete, or when it is installed in attics or crawlspaces that are not used for storage or as living space.
In order to be considered an appropriate thermal barrier, a material has to have been shown to resist fire for 15 minutes. Half-inch drywall meets this specification, as do some sprayed cellulose materials and cement-based plasters.
Thermal Barriers vs. Ignition Barriers
Another term that you may see used in building codes related to spray foam insulation is "ignition barrier." Ignition barriers are not as fire-resistant as thermal barriers. They're required in attic storage spaces. Approved ignition barriers include 1/4-inch wood structural panels, 3/8-inch gypsum, 3/8-inch particleboard, and 0.016-inch thick corrosion-resistant steel.
Those who seek spray foam training and support from NCFI have the opportunity to learn more about the requirements for thermal barriers and other building codes related to spray foam. If you're seeking training and support from NCFI, visit our website to learn more about our certification programs for applicators.