Uses
Batts of fiberglass insulation come in many different lengths, thicknesses and widths. Each size is meant for a specific application, with smaller, thinner batts used for most residential applications. Large buildings, including offices and warehouses that are built with metal framework, may require a batt that is slightly larger or thicker. Similarly, floors and ceilings also benefit from fiberglass insulation batts that are wider, longer or thicker.
Density
The thickness, length and width of each insulation batt are the primary factors in determining its R-value, which is the amount of thermal resistance provided by that insulation. Standard insulation batts meant for use in metal frame construction, as well as those for wood-framed walls, are available in thicknesses of 3.5 inches, 5.5 inches and 6.25 inches. Insulation batts for wood-framed floors and ceilings are available in thicknesses of 6.25 inches, 6.75 inches, 8 inches, 8.25 inches, 9.5 inches, 10.25 inches and 12 inches.
Length
Fiberglass insulation is available in different lengths, which makes it easy to fill cavities that are long or short. The longest fiberglass insulation batts are 96 inches, but these are typically reserved for metal framing. Batts are also available in lengths of 48 inches and 93 inches, which are better suited for residential applications.
Rolls of fiberglass insulation are sometimes used, particularly when insulating ceiling cavities and between high walls. These rolls are typically found in lengths of 17.5 feet, 24 feet, 25 feet, 32 feet, 39 feet, 40 feet, 48 feet, 62 feet, 70.5 feet or 80 feet. Rolls can be specially ordered at lengths of 90 feet or 104 feet.
Width
Just as fiberglass insulation is available in different thicknesses and lengths, it is also available in different widths. Common batt widths in metal frame applications include 16 inches and 24 inches, while widths for residential construction include 15 inches and 23 inches. Fiberglass batts meant for use in roofs, ceilings and floors are available in several different sizes, including 15 inches, 15.5 inches, 16 inches, 23 inches, 23.75 inches and 24 inches.