Foil Building Products

Practically every building-product application of aluminum of foil is concerned with insulation of space, and/or with vapor barrier functions in a variety of situations. A few other uses are concerned with component structure (e.g., honeycomb materials).

Typical aluminum foil building products include wall, ceiling and floor insulation; water vapor barrier (e.g., laminations of foil/paper applied to wall surfaces, or wrapped over insulation batting around pipes or ducts carrying fluids or air); foil-backed building board; built-up siding and roofing; light and heat reflectors; heat dissipaters; and foil/fiber air duct material, where foil is applied to the outer surfaces (and sometimes also inner surfaces) of rigid fibre duct components.

Insulation Applications: The principal types of aluminum foil insulation products include foil/spun glass; foil/foam; foil/fiberboard; foil/paper air-space blankets; and foil-rock wool. These are used in nearly every part of the world in both houses and commercial buildings, as well as house trailers, trucks, busses, rail cars, boats and ships, and cold storage plants.

Alone, aluminum foil insulates (where it is a boundary of, or encloses, an air space) by reducing heat transfer through radiation. It does this by reflecting about 96% of the infra-red heat waves striking its surface and emitting (radiating) only four percent. Thickness of the aluminum has no effect on its insulating properties. Reduction in brightness through exposure encountered in normal installation also has little effect (about one or two percent). Since aluminum is also an excellent conductor of heat, the foil must be installed so that the reflective surface is separated from the surface of the adjacent building material by an air space of at least 3/4 inch in walls and by as much, and preferably more space, in ceilings.

The foil/glass fibre types have paper-backed foil on one or both sides of the glass bat. The inter-folded types of foil building insulation generally are made of a foil/kraft/foil lamination, folded and joined with glue to form a cross section of two or three rectangular compartments when the material is "expanded" and placed between building studs or beams. These layers of dead air space, plus the high reflectivity of the foil, combine to retain heat in the protected areas.