batt

Batt insulation, commonly called batts, is a pre-cut, flexible blanket of fibrous insulating material used to fill cavities between structural members such as studs and joists. It is installed in walls, ceilings, attics, and floors to reduce heat transfer and improve energy efficiency. The material is typically fiberglass or mineral wool, and some batts may include natural fibers or other binders.

Most batt insulation comes in widths designed to fit standard stud spacings, such as 16 or 24 inches on center in North America and 400 or 600 mm in many other regions. The thickness matches the cavity depth, with common options around 3.5 inches for 2x4 walls and 5.5 inches for 2x6 walls. Batts may be unfaced or faced with a paper, kraft, or foil layer. Facing can serve as a vapor retarder and helps hold the batts in place during installation.

Materials commonly used include fiberglass and mineral wool. Fiberglass batts are made from recycled glass and other fibers, while mineral wool batts use rock or slag wool and are generally more resistant to fire and moisture. The performance of batt insulation is described by R-value, which increases with thickness and is influenced by the material type; fiberglass batts typically provide about 3 to 4 per inch, while mineral wool lies around 3 per inch.

Installation considerations include ensuring a snug fit without excessive compression, cutting batts to fit around electrical boxes and other obstructions, and maintaining any required vapor barriers on the warm side of the assembly. Gaps, voids, or compression reduce effectiveness and can lead to drafts or moisture issues. Batts are usually cost-effective and easy to install for standard cavities, but irregular spaces may require alternative insulation methods.