Wall Cavity Insulation in Zone 2 (Hot)
The DOE recommends R-13 for wall cavity insulation in Climate Zone 2 (Hot). This zone has 2,000 heating degree days and 3,500 cooling degree days annually. The typical wall cavity cavity depth is 3.5 inches. States in Zone 2 include Alabama, Arizona, Florida, Georgia, Louisiana and 2 more.
Quick Facts
Insulation Comparison for Wall Cavity in Zone 2
The table below compares all insulation types for achieving R-13 in the wall cavity of a building in Zone 2 (Hot). Types marked "Recommended" are specifically suited for wall cavity applications. Material costs are shown per square foot and per 1,000 square feet for easy budgeting. Labor costs typically add 30 to 100 percent to material costs depending on the insulation type and project complexity.
| Insulation Type | R/Inch | Thickness | $/SqFt | $/1000 SqFt | Fits | Rec. |
|---|---|---|---|---|---|---|
| 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 2 can be achieved with standard fiberglass or mineral wool batts in a 2x4 wall. Ensure complete cavity fill without compression — batts should be cut to fit snugly around wires, pipes, and electrical boxes rather than being compressed or leaving voids. In hot climates, wall insulation helps keep conditioned cool air inside during summer. Proper installation prevents convective loops within the cavity that can transport heat and moisture. For existing homes without wall insulation, blown-in cellulose or fiberglass through small exterior holes is the most practical retrofit approach and can reduce heating and cooling costs by 20 to 30 percent while dramatically improving comfort.
States in Zone 2
The following states include areas within Climate Zone 2. Click any state to see its complete insulation requirements across all applicable zones.