Climate zone 2B: hot-dry
The low deserts of Arizona and California: extreme summer heat with dry air.
Zone 2B covers 20 counties in 3 states, home to about 6,815,737 people (FEMA NRI population). ENERGY STAR’s target for an uninsulated attic here is R49; with 3–4 inches already in place, add to R38.
Insulation targets for zone 2B
| Where | Guidance |
|---|---|
| Attic, uninsulated | R49 |
| Attic, 3–4 inches already | R38 |
| 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 2B 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 “B” (dry) regime means low humidity, high sun and often hard water: sealants, roof coverings and water-using appliances wear faster.
Largest counties in zone 2B
States in this zone: Texas (14), Arizona (5), California (1).