Climate Zone 1 — Hot-Humid
Zone 1 covers the southernmost and most tropical areas of the United States, including southern Florida, Hawaii, and US territories in the Caribbean and Pacific. These regions experience extremely high humidity levels year-round combined with consistently warm temperatures. The primary energy concern in Zone 1 is cooling rather than heating, so insulation strategies focus on reducing heat gain from the roof and exterior walls. Air sealing is especially critical in this climate to prevent moisture-laden outdoor air from infiltrating the building envelope and causing condensation problems.
Zone 1 Climate Data
R-Value Requirements for Zone 1
The table below lists the DOE recommended insulation R-values for every building component in Climate Zone 1 (Hot-Humid). 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-30 | 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 1 Attic (R-30)
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-30 recommendation for Zone 1 attics, along with the estimated material cost per square foot.
| Insulation Type | R/Inch | Thickness Needed | Cost/SqFt | DIY? |
|---|---|---|---|---|
| Fiberglass Batt | R-3.2 | 9.4" | $3.60 | Yes |
| Blown-In Fiberglass | R-2.5 | 12" | $2.40 | Pro |
| Blown-In Cellulose | R-3.5 | 8.6" | $2.10 | Yes |
| Open-Cell Spray Foam | R-3.7 | 8.1" | $12.00 | Pro |
| Closed-Cell Spray Foam | R-6.5 | 4.6" | $24.00 | Pro |
| Mineral Wool Batt | R-3.3 | 9.1" | $4.50 | Yes |
| Mineral Wool Board | R-4.3 | 7" | $7.50 | Yes |
| Extruded Polystyrene (XPS) | R-5 | 6" | $5.40 | Yes |
| Expanded Polystyrene (EPS) | R-3.9 | 7.7" | $3.60 | Yes |
| Polyisocyanurate (Polyiso) | R-6 | 5" | $6.60 | Yes |
| Cotton Denim (Recycled) | R-3.5 | 8.6" | $6.00 | Yes |
| Sheep Wool | R-3.5 | 8.6" | $10.50 | Yes |
| Aerogel Blanket | R-10 | 3" | $90.00 | Yes |
| Vermiculite (Loose Fill) | R-2.1 | 14.3" | $3.00 | Yes |
Insulation Strategy for Zone 1
In Zone 1, the primary insulation strategy focuses on reducing solar heat gain through the roof. Attic insulation at R-30 combined with a radiant barrier can significantly reduce cooling costs. Wall insulation at R-13 is sufficient because the temperature differential between indoors and outdoors is relatively small during the mild winter months. Air sealing is critical in this humid climate to prevent moisture-laden outdoor air from infiltrating the building envelope, which can cause condensation and mold growth inside wall cavities. Consider light-colored roofing materials and properly ventilated attic spaces to further reduce cooling loads. Continuous exterior wall insulation is not required in this zone, keeping construction costs lower while still achieving adequate thermal performance for the climate.
States in Climate Zone 1
The following states include areas that fall within DOE Climate Zone 1. 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.