Editing Glass wool (section)

==Fiberglass batts and blankets==
[[File:CSIRO ScienceImage 2175 Installing Insulation Batts.jpg|thumb|Installing glass wool batts as ceiling insulation]]
Batts are precut, whereas blankets are available in continuous rolls. Compressing the material reduces its effectiveness. Cutting it to accommodate electrical boxes and other obstructions allows air a free path to cross through the wall cavity. One can install batts in two layers across an unfinished attic floor, perpendicular to each other, for increased effectiveness at preventing [[heat bridging]]. Blankets can cover [[joist]]s and studs as well as the space between them. Batts can be challenging and unpleasant to hang under floors between joists; straps, or staple cloth or wire mesh across joists, can hold it up.

Gaps between batts (bypasses) can become sites of air infiltration or condensation (both of which reduce the effectiveness of the insulation) and require strict attention during the installation. By the same token careful [[weatherization]] and installation of [[vapour barriers]] is required to ensure that the batts perform optimally. Air infiltration can be also reduced by adding a layer of cellulose loose-fill on top of the material.