Climate Zone 5A - Cool, Humid
Warm summers and cold winters with humidity. Heating loads dominate. This climate zone encompasses parts of Illinois, Indiana, Ohio, Pennsylvania, New York, Connecticut, Massachusetts and includes major cities like Chicago, Indianapolis, Columbus, Philadelphia.
Common Questions About Zone 5A
Zone 5A definition
This page explains what IECC climate zone 5A means in HVAC and building-code terms.
Cities in zone 5A
Use the city examples below to answer common lookup searches for this zone.
Heating and cooling profile
See whether zone 5A 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 5A Means
Temperature class
Cool (Zone 5)
Moisture class
Moist (A)
Load priority
Heating-dominant
Quick definition
Warm summers and cold winters with humidity. Heating loads dominate.
Common City Lookups for Zone 5A
| City | IECC zone answer | Why it matters |
|---|---|---|
| Chicago | Chicago is commonly treated as IECC climate zone 5A in this guide. | High heating loads |
| Indianapolis | Indianapolis is commonly treated as IECC climate zone 5A in this guide. | High heating loads |
| Columbus | Columbus is commonly treated as IECC climate zone 5A in this guide. | High heating loads |
| Philadelphia | Philadelphia is commonly treated as IECC climate zone 5A in this guide. | High heating loads |
| Boston | Boston is commonly treated as IECC climate zone 5A in this guide. | High heating 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
- •High heating loads
- •Moderate cooling needs
- •Freeze protection critical
- •Humidity control
- •Snow load considerations
Common Equipment
- ✓Gas furnaces with AC
- ✓Boilers with separate cooling
- ✓Heat pumps with backup
- ✓High-efficiency systems
Energy Code Requirements
Equipment Efficiency
- ⚠SEER 13+ minimum
- ⚠HSPF 7.7+ for heat pumps
- ⚠AFUE 80+ for furnaces
- ⚠Enhanced building envelope
Insulation Requirements
Major Cities in Zone 5A
States with Zone 5A Areas
Quick Reference
Calculate Load
Use our load calculators with the design temperatures and requirements specific to Zone 5A.