Wall (Cavity Wall) Insulation: Definition and What it is
Insulation installed in wall cavities between studs to reduce heat transfer.
What is Wall (Cavity Wall) Insulation?
Wall insulation fills the cavities between wall studs to reduce heat transfer through exterior walls. Proper wall insulation can reduce heating and cooling costs by 15-20% while improving comfort by eliminating cold spots and drafts.
Wall cavities in typical 2x4 construction provide 3.5 inches of insulation space, while 2x6 walls provide 5.5 inches. The insulation fills this space to slow heat transfer between conditioned interior space and the outdoors. Different materials and installation methods suit new construction versus retrofit applications. New construction allows easy installation of batts or spray foam before drywall goes up. Retrofit insulation requires dense-pack blown cellulose or injection foam through small holes drilled in exterior or interior walls.
Wall Insulation Options
- Fiberglass Batts: R-13 to R-15 in 2x4 walls, R-19 to R-21 in 2x6 walls, best for new construction
- Dense-Pack Cellulose: R-13 to R-15 in 2x4 walls, ideal for retrofit applications, provides air sealing
- Spray Foam: Open-cell for interior walls, closed-cell for exterior, superior air sealing
- Mineral Wool Batts: Excellent fire resistance and soundproofing, easy installation
Wall Insulation Best Practices
For new construction, install batts carefully without compression or gaps, split around wiring and pipes, and use proper vapor barrier placement for your climate. Consider upgrading to 2x6 framing for higher R-values. For retrofits, dense-pack cellulose provides excellent performance and air sealing through minimal disruption. Always address air sealing at top and bottom plates, around windows and doors, and at penetrations. In cold climates, ensure proper vapor barrier placement to prevent condensation within wall cavities. Consider exterior continuous insulation for maximum performance.
Benefits of Wall (Cavity Wall) Insulation
- Reduce heating and cooling costs by 15-20%
- Improve comfort and eliminate cold spots near exterior walls
- Reduce outdoor noise transmission
- Prevent ice dams by reducing heat loss through walls
- Increase home value and energy efficiency ratings
- Essential for creating comfortable, energy-efficient homes
Wall (Cavity Wall) Insulation Cost
Wall insulation costs vary significantly between new construction and retrofit applications.
- New construction batts ($0.50-$1.50/sq ft); retrofit dense-pack ($2-$4/sq ft)
- Material type (spray foam costs significantly more)
- Wall cavity depth and target R-value
- Total square footage of exterior walls
- Access and retrofit complexity
- Regional labor and material costs
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