Basement Wall Insulation in Zone 1 (Hot-Humid)
The DOE recommends None required for basement wall insulation in Climate Zone 1 (Hot-Humid). This zone has 500 heating degree days and 5,000 cooling degree days annually. The typical basement wall cavity depth is 4 inches. States in Zone 1 include Florida, Hawaii.
Quick Facts
Insulation Not Required
The DOE does not require basement wall insulation in Climate Zone 1 (Hot-Humid). The moderate climate in this zone does not create sufficient temperature differentials across this building component to justify the cost of insulation. However, local building codes may have different requirements, and adding insulation may still provide comfort benefits, noise reduction, and improved indoor air quality. Some utility programs and green building certifications may incentivize or require insulation for this component even in Zone 1.
If you choose to add insulation despite it not being required, even a modest R-5 to R-10 can improve comfort by reducing temperature differences between rooms and eliminating cold or hot spots on surfaces adjacent to unconditioned spaces. The cost of adding insulation during new construction is minimal compared to the total project cost, so many builders include it regardless of the code requirement.
Installation Guidance
Basement wall insulation is not required by the DOE in Climate Zone 1 due to the moderate ground temperatures and limited heating loads. However, insulating basement walls can still improve comfort and reduce energy costs if the basement is used as living space. If you choose to insulate, use moisture-resistant materials such as rigid XPS foam or closed-cell spray foam. Even R-5 to R-8 of rigid foam on the basement walls can noticeably improve comfort and reduce humidity levels in the basement space.
States in Zone 1
The following states include areas within Climate Zone 1. Click any state to see its complete insulation requirements across all applicable zones.