Flammability Of Attic Insulation

While mineral based insulation materials are non combustible or low in combustibility the paper or foil backing surrounding the insulating material may be flammable.

Flammability of attic insulation.

Cellulose smolders slowly when it starts to burn and if installed too close to an ignition source like a gas flue or recessed light fixture will eventually ignite and can spread to start a larger fire in nearby materials that are more flammable. If you ve got spray foam insulation in an attic for example it s probably already separated from the living space by a thermal barrier. But it is combusible which means capable of being ignited. This therefore acts as a great substance to reducing the rate of flames spreading.

Insulation backing materials should be fire retardant and have a maximum flame spread rating of 25 when tested in accordance with astm e 84 standard test method for surface burning characteristics of building materials published by the american society for testing materials astm and as required by ul 723 standard for. Insulation flammability isn t an issue with all recessed lighting fixtures though. The main issue that arises is that many people will apply vapor retardant to the surface and the vapor retardants that are commonly used are flammable. Many manufacturers make it clear that their radiant barrier material has a class a fire rating meaning that their radiant barrier insulation meets the fire and smoke safety requirements of building codes.

If a home has spray foam insulation in an attic or crawl space the building code requires using materials or assemblies that offer some fire resistance but not as much as is required for a thermal barrier. The most flammable insulation materials is cellulose. Also referred to as loose fill cellulose insulation the small cellulose particles are flammable and can ignite if they re directly exposed to an overheated recessed can or electrical spark. Which is impressive in comparison to traditional insulation which are more prone to fires and contribute to the fire spread.

Insulation such as icynene spray foam is fire retardant. If a fixture isn t rated for insulation contact no insulation should come within 3 inches of the fixture and. Fiberglass is an inorganic material and as such is a noncombustible insulation material that is not flammable. The flammability of radiant barrier insulation depends on the manufacturer.