Climate Zone 2 — Hot
Zone 2 encompasses the Gulf Coast states, southern Texas, and parts of the desert Southwest including the lower elevations of Arizona. These areas experience long, hot summers with significant cooling loads and relatively mild winters. The balance between heating and cooling shifts heavily toward cooling in this zone, though occasional winter cold snaps can occur. Insulation in Zone 2 helps keep conditioned air inside during the hot months and provides moderate protection during brief cold periods. Radiant barriers in the attic are particularly effective in this zone due to the intense solar radiation.
Zone 2 Climate Data
R-Value Requirements for Zone 2
The table below lists the DOE recommended insulation R-values for every building component in Climate Zone 2 (Hot). Click on any component to see detailed insulation type comparisons, thickness requirements, and cost estimates specific to that component in this climate zone.
| Building Component | Required R-Value | Details |
|---|---|---|
| Attic | R-38 | View insulation options → |
| Wall Cavity | R-13 | View insulation options → |
| Wall Continuous | None required | View insulation options → |
| Floor | R-13 | View insulation options → |
| Basement Wall | None required | View insulation options → |
| Crawlspace | None required | View insulation options → |
| Cathedral Ceiling | R-22 | View insulation options → |
| Garage Ceiling | R-19 | View insulation options → |
Insulation Thickness by Type for Zone 2 Attic (R-38)
The attic is typically the most cost-effective location for insulation in any climate zone. The table below shows the thickness of each insulation type needed to achieve the R-38 recommendation for Zone 2 attics, along with the estimated material cost per square foot.
| Insulation Type | R/Inch | Thickness Needed | Cost/SqFt | DIY? |
|---|---|---|---|---|
| Fiberglass Batt | R-3.2 | 11.9" | $4.56 | Yes |
| Blown-In Fiberglass | R-2.5 | 15.2" | $3.04 | Pro |
| Blown-In Cellulose | R-3.5 | 10.9" | $2.66 | Yes |
| Open-Cell Spray Foam | R-3.7 | 10.3" | $15.20 | Pro |
| Closed-Cell Spray Foam | R-6.5 | 5.8" | $30.40 | Pro |
| Mineral Wool Batt | R-3.3 | 11.5" | $5.70 | Yes |
| Mineral Wool Board | R-4.3 | 8.8" | $9.50 | Yes |
| Extruded Polystyrene (XPS) | R-5 | 7.6" | $6.84 | Yes |
| Expanded Polystyrene (EPS) | R-3.9 | 9.7" | $4.56 | Yes |
| Polyisocyanurate (Polyiso) | R-6 | 6.3" | $8.36 | Yes |
| Cotton Denim (Recycled) | R-3.5 | 10.9" | $7.60 | Yes |
| Sheep Wool | R-3.5 | 10.9" | $13.30 | Yes |
| Aerogel Blanket | R-10 | 3.8" | $114.00 | Yes |
| Vermiculite (Loose Fill) | R-2.1 | 18.1" | $3.80 | Yes |
Insulation Strategy for Zone 2
Zone 2 insulation strategies balance moderate cooling loads against occasional heating demands. Attic insulation at R-38 provides a significant step up from Zone 1 and pays for itself quickly through reduced air conditioning costs. A radiant barrier in the attic remains highly effective in this zone due to intense solar radiation during summer months. Wall cavity insulation at R-13 using fiberglass batts or blown-in cellulose is the standard approach. In this zone, pay special attention to duct insulation and sealing, as ductwork in unconditioned attics can account for 20-30 percent of total cooling energy if not properly insulated and sealed. The relatively mild winters mean that floor and basement insulation requirements remain modest.
States in Climate Zone 2
The following states include areas that fall within DOE Climate Zone 2. Note that many states span multiple climate zones, so specific locations within a state may have different insulation requirements. Click any state to see the specific zones that apply and the complete insulation recommendations for each area.
Other Climate Zones
Compare insulation requirements across climate zones to understand how your location's needs compare to other regions. Each zone page includes complete R-value tables, state listings, and insulation strategies.