Cavity insulation is thermal material installed within the hollow spaces (cavities) between wall studs, floor joists, or ceiling framing to reduce heat transfer through the building envelope. This method fills existing air gaps with insulation products, improving thermal resistance without expanding the wall thickness.
Materials and Installation Methods
Cavity insulation includes fiberglass batts, blown-in cellulose, mineral wool, and spray foam. Fiberglass batts are installed between studs at standard 16 or 24-inch spacing. Blown-in insulation uses pneumatic equipment to fill cavities, achieving uniform density. Typical cavities in residential construction are 3.5 inches (2×4 walls) or 5.5 inches (2×6 walls), accommodating R-11 to R-21 insulation.
Effectiveness and Limitations
Cavity insulation is cost-effective at $0.50-1.50 per square foot and reduces thermal bridging through studs. However, wood framing typically provides only R-1 per inch, so cavity insulation alone doesn’t achieve high performance targets. Thermal bridges reduce overall wall R-value by 15-25 percent. Proper air sealing and continuous insulation layers improve overall wall system performance.