Wall Continuous (Exterior) Insulation in Zone 5 (Cool)
The DOE recommends R-5 for wall continuous (exterior) insulation in Climate Zone 5 (Cool). This zone has 6,500 heating degree days and 800 cooling degree days annually. The typical wall continuous (exterior) cavity depth is 2 inches. States in Zone 5 include Arizona, California, Colorado, Connecticut, Idaho and 25 more.
Quick Facts
Insulation Comparison for Wall Continuous (Exterior) in Zone 5
The table below compares all insulation types for achieving R-5 in the wall continuous (exterior) of a building in Zone 5 (Cool). Types marked "Recommended" are specifically suited for wall continuous (exterior) 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. |
|---|---|---|---|---|---|---|
| Expanded Polystyrene (EPS) | R-3.9 | 1.3" | $0.60 | $600 | Yes | Yes |
| Extruded Polystyrene (XPS) | R-5 | 1" | $0.90 | $900 | Yes | Yes |
| Polyisocyanurate (Polyiso) | R-6 | 0.8" | $1.10 | $1,100 | Yes | Yes |
| Mineral Wool Board | R-4.3 | 1.2" | $1.25 | $1,250 | Yes | Yes |
| Aerogel Blanket | R-10 | 0.5" | $15.00 | $15,000 | Yes | Yes |
| Blown-In Cellulose | R-3.5 | 1.4" | $0.35 | $350 | Yes | - |
| Blown-In Fiberglass | R-2.5 | 2" | $0.40 | $400 | Yes | - |
| Vermiculite (Loose Fill) | R-2.1 | 2.4" | $0.50 | $500 | No | - |
| Fiberglass Batt | R-3.2 | 1.6" | $0.60 | $600 | Yes | - |
| Mineral Wool Batt | R-3.3 | 1.5" | $0.75 | $750 | Yes | - |
| Cotton Denim (Recycled) | R-3.5 | 1.4" | $1.00 | $1,000 | Yes | - |
| Sheep Wool | R-3.5 | 1.4" | $1.75 | $1,750 | Yes | - |
| Open-Cell Spray Foam | R-3.7 | 1.4" | $2.00 | $2,000 | Yes | - |
| Closed-Cell Spray Foam | R-6.5 | 0.8" | $4.00 | $4,000 | Yes | - |
Installation Guidance
Continuous exterior wall insulation at R-5 in Zone 5 is critical for addressing thermal bridging through wood framing. At R-5, you need approximately 1 inch of rigid foam (XPS at R-5/inch or polyiso at R-6/inch) or 1.25 inches of mineral wool board. Attach the insulation to the wall sheathing using adhesive compatible with the foam type and mechanical fasteners as needed. Install furring strips over the insulation for cladding attachment — 1x3 or 1x4 wood strips screwed through the insulation into the studs with long structural screws provide a solid nailing base for siding. Ensure that window and door jamb extensions accommodate the additional wall thickness. Flash all openings with self-adhered membrane that bridges from the window frame across the insulation to the water-resistive barrier on the sheathing. In Zone 5, the continuous insulation keeps the wall sheathing warmer, reducing the risk of condensation and improving the long-term durability of the wall assembly.
States in Zone 5
The following states include areas within Climate Zone 5. Click any state to see its complete insulation requirements across all applicable zones.