Climate Zone 1B - Very Hot, Dry
Very hot summers with low humidity. Extreme temperature swings between day and night. This climate zone encompasses parts of Arizona, California, Nevada, Texas and includes major cities like Phoenix, Tucson, Las Vegas, Palm Springs.
Common Questions About Zone 1B
Zone 1B definition
This page explains what IECC climate zone 1B means in HVAC and building-code terms.
Cities in zone 1B
Use the city examples below to answer common lookup searches for this zone.
Heating and cooling profile
See whether zone 1B is heating-dominant, cooling-dominant, or balanced.
HVAC requirements
Compare design temperatures, degree days, code requirements, and equipment guidance for this zone.
What IECC Climate Zone 1B Means
Temperature class
Very Hot (Zone 1)
Moisture class
Dry (B)
Load priority
Cooling-dominant
Quick definition
Very hot summers with low humidity. Extreme temperature swings between day and night.
Common City Lookups for Zone 1B
| City | IECC zone answer | Why it matters |
|---|---|---|
| Phoenix | Phoenix is commonly treated as IECC climate zone 1B in this guide. | Extreme cooling loads |
| Tucson | Tucson is commonly treated as IECC climate zone 1B in this guide. | Extreme cooling loads |
| Las Vegas | Las Vegas is commonly treated as IECC climate zone 1B in this guide. | Extreme cooling loads |
| Palm Springs | Palm Springs is commonly treated as IECC climate zone 1B in this guide. | Extreme cooling loads |
Design Temperatures
Winter Design Temperatures
Used for heating load calculations and equipment sizing
Summer Design Temperatures
Used for cooling load calculations and equipment sizing
Heating & Cooling Degree Days
Heating Degree Days (HDD)
Base 65°F. Higher numbers indicate more heating requirements and longer heating seasons.
Cooling Degree Days (CDD)
Base 65°F. Higher numbers indicate more cooling requirements and longer cooling seasons.
HVAC System Considerations
Key Considerations
- •Extreme cooling loads
- •UV protection critical
- •Dust filtration important
- •Equipment derating for high temps
- •Large temperature swings
Common Equipment
- ✓High-capacity air conditioners
- ✓Evaporative cooling (swamp coolers)
- ✓Two-stage or variable speed systems
- ✓Heat pumps with auxiliary heat
Energy Code Requirements
Equipment Efficiency
- ⚠SEER 14+ minimum
- ⚠High-performance fenestration
- ⚠Radiant barrier requirements
- ⚠Duct insulation R-8 minimum
Insulation Requirements
Major Cities in Zone 1B
States with Zone 1B Areas
Quick Reference
Calculate Load
Use our load calculators with the design temperatures and requirements specific to Zone 1B.