Zone 6 Wall Cavity Insulation — R-13
The DOE recommends R-13 insulation for the wall cavity in Climate Zone 6 (Cold). The typical wall cavity cavity depth is 3.5 inches. This page compares all insulation types showing the thickness needed, material cost per square foot, and whether each type fits within the standard cavity depth.
Quick Summary
Insulation Type Comparison for Zone 6 Wall Cavity
The following table compares all insulation types for achieving R-13 in the wall cavity of a building in Climate Zone 6. Types marked as "recommended" are specifically suited for this building component. The cost estimates represent material costs only and do not include labor, which can add 30-100% depending on the insulation type and project complexity.
| Insulation Type | R/Inch | Thickness | Cost/SqFt | Cost/1000 SqFt | Fits Cavity | Recommended |
|---|---|---|---|---|---|---|
| Blown-In Cellulose | R-3.5 | 3.7" | $0.91 | $910 | No | Yes |
| Blown-In Fiberglass | R-2.5 | 5.2" | $1.04 | $1,040 | No | Yes |
| Fiberglass Batt | R-3.2 | 4.1" | $1.56 | $1,560 | No | Yes |
| Mineral Wool Batt | R-3.3 | 3.9" | $1.95 | $1,950 | No | Yes |
| Cotton Denim (Recycled) | R-3.5 | 3.7" | $2.60 | $2,600 | No | Yes |
| Sheep Wool | R-3.5 | 3.7" | $4.55 | $4,550 | No | Yes |
| Open-Cell Spray Foam | R-3.7 | 3.5" | $5.20 | $5,200 | No | Yes |
| Closed-Cell Spray Foam | R-6.5 | 2" | $10.40 | $10,400 | Yes | Yes |
| Aerogel Blanket | R-10 | 1.3" | $39.00 | $39,000 | Yes | Yes |
| Vermiculite (Loose Fill) | R-2.1 | 6.2" | $1.30 | $1,300 | No | - |
| Expanded Polystyrene (EPS) | R-3.9 | 3.3" | $1.56 | $1,560 | Yes | - |
| Extruded Polystyrene (XPS) | R-5 | 2.6" | $2.34 | $2,340 | Yes | - |
| Polyisocyanurate (Polyiso) | R-6 | 2.2" | $2.86 | $2,860 | Yes | - |
| Mineral Wool Board | R-4.3 | 3" | $3.25 | $3,250 | Yes | - |
Installation Guidance
Wall cavity insulation at R-13 in Zone 6 is the standard approach for residential wall assemblies. In 2x4 framing (3.5-inch cavity), fiberglass batts provide approximately R-13, which is the most common wall cavity insulation used in residential construction. For 2x6 framing (5.5-inch cavity), R-20 fiberglass or mineral wool batts are available and recommended in colder zones even though the minimum cavity requirement is R-13. The quality of batt installation dramatically affects real-world performance — Grade I installation per RESNET standards requires complete cavity fill with no visible gaps or compression. Dense-pack cellulose blown into wall cavities is an excellent alternative that provides superior air sealing compared to batts. In existing homes, blown-in cellulose or fiberglass can be installed through small holes drilled in the sheathing without removing interior finishes.
Construction Notes
Standard 2x4 wall framing provides a 3.5-inch cavity depth, while 2x6 framing provides 5.5 inches. Wall cavity insulation is installed between the studs and must fill the entire cavity without gaps, voids, or compression. In new construction, batt or spray foam insulation is installed before drywall. In existing homes, blown-in cellulose or fiberglass can be dense-packed through small holes drilled in the exterior sheathing or interior drywall. Proper installation is critical for wall cavity insulation because every gap or void creates a thermal bypass. Grade I installation per RESNET standards requires that insulation fills 100 percent of the cavity with no visible gaps when viewed from the face.