Fiberglass Batt Insulation
Fiberglass batt insulation has historically been the most commonly insulation material installed in building in the US. Fiberglass is made from molten glass and comes in a batt form cut to fit the cavity.
Fiberglass Batt insulation has an R-value of approximately 3.5 per inch, although there are dense batts with a higher R-value. Gaps between the batts and the framing can cause air infiltration. Also, the material itself is not a vapor or air barrier and allows air and moisture to pass through it. For this reason, fiberglass batts installed in the exterior shell of a building need to be covered with a vapor barrier. In New England this barrier needs to be installed facing the interior of the building. Due to the air infiltration, fiberglass batts installed in a roof system, need to have proper venting to prevent ice dams and condensation. Fiberglass Batts, while not as effective as cellulose or mineral wool, can be used for sound deadening as well.