Air leakage rate defined as the number of air changes per hour that occur in a building. This is determined with a blower door with a 50 pascal pressure difference between the inside and outside of a building and then extrapolated for the natural building pressures that occur annually.

An air barrier is, as it sounds, any physical barrier devoid of holes, cracks, penetrations, etc., that physically prevents the movement of air.

Air infiltration refers to either the process of unconditioned air entering a conditioned space (e.g., outside air entering a building) or conditioned air migrating to an unconditioned space (e.g., heated air migrating to an attic or to the outdoors.) Air drives change with the seasons, and are affected by variables such as air pressures and wind, but as a rule, air will move from the hot side to the cold side, so for example, in winter air is more likely to move from the interior to the exterior, while in the summer the reverse is true. Air infiltration is a direct result of several factors, including unsealed penetrations (joints, cracks, and holes), insulation materials of insufficient density to effectively limit or prevent infiltration, poor installation, lack of air sealing, etc. Air infiltration is one of the four ways that heat moves through a structure (See also conduction, radiation and convection)

The process by which very small holes, cracks, penetrations and joints which could allow the passage of air from the interior to the exterior, or vice versa, or between areas of a building (such as living space to attic space) are sealed or closed off, using caulking, canned foams, etc. Proper air sealing should precede any insulation job.

An inorganic salt often used to reduce the amount of borate needed to achieve a Class A fire rating in cellulose insulation. Ammonium sulfate may, in the presence of sufficient moisture, produce ammonia smells and lead to the corrosion of metal pipes, fasteners, etc. National Fiber’s Cel-Pak and Nu-Wool insulations are all borate formulations and use NO ammonium sulfate.

In terms of structures and insulation, the use of the words assembly or assemblies refers to any enclosed space that can effectively contain insulation. For example, a stud bay in a wall will be bounded by a top and bottom plate, sheathing on the exterior and wallboard on the interior, forming an assembly. The same would hold true for a rafter bay in a cathedral ceiling. Both of these would be referred to as ‘assemblies’.

American Society for Testing and Materials - ASTM International is one of the largest voluntary standards development organizations in the world and a source for technical standards for materials, products, systems, and services.

A test method using flame spread & smoke developed densities designed to measure the relative burning behavior of a material. Materials with lower flame spread and smoke developed values are considered more 'fire safe' since they would give occupants a better chance of escaping a fire.

The gradual loss in intensity of any kind of flux through a medium. Examples: sunlight is attenuated by dark glasses, X-rays are attenuated by lead and sound is attenuated by dense-packed cellulose insulation.