Climate zone 1A: very hot-humid
South Florida, Hawaii and the territories: almost no heating season and year-round humidity.
Zone 1A covers 12 counties in 3 states, home to about 8,972,892 people (FEMA NRI population). ENERGY STAR’s target for an uninsulated attic here is R30; with 3–4 inches already in place, add to R25.
Insulation targets for zone 1A
| Where | Guidance |
|---|---|
| Attic, uninsulated | R30 |
| Attic, 3–4 inches already | R25 |
| Floor over unheated space | R13 |
| Walls | No added exterior sheathing listed for zones 1–2; insulate empty wall cavities when siding is off. |
| Basement or crawlspace walls | No basement or crawlspace wall value listed for zones 1–2. |
Homeowner retrofit guidance, not your local code. Your jurisdiction may enforce an older or amended IECC; ask the building department before a permit job.
What it means for upkeep
Most zone 1A counties fall in the hot-humid Building America region. Long cooling season, heavy humidity and the Atlantic hurricane season set the calendar: drains, dehumidifying and storm prep.
The “A” (moist) regime means humidity drives much of the care: drains, dehumidifying and keeping crawlspaces and basements dry.
Largest counties in zone 1A
States in this zone: Hawaii (5), Florida (4), Texas (3).