Term Description
Air-impermeable insulation

An insulation having an air permeance equal to or less than 0.02 L/s-m2 at 75 Pa pressure differential tested according to ASTM E2178 or E283.

Blanket insulation

Fiberglass or other compressible fibrous insulation, generally available in roll form.

Cellular glass insulation

A rigid closed-cell insulation board made from crushed glass and hydrogen sulfide gas.

Composite board roof insulation

Rigid board insulation generally composed of perlite, wood fiberboard, oriented strand board or plywood factory-bonded to polyisocyanurate or polystyrene.

Exterior insulation and finish system (EIFS)

A non-load-bearing outdoor wall finish system consisting of a thermal insulation board, attachment system, reinforcement system and compatible finish.

Fiberglass insulation

Blanket or rigid board insulation composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls.


Any of a variety of materials designed to reduce the flow of heat from or into a building. See "thermal insulation."

Tapered insulation

A system of precut or premolded insulation boards or a poured insulation fill designed to provide slope to the roof deck before installing the roof membrane.

Thermal insulation

A material applied to reduce the flow of heat.