Climate Zone 4A - Mixed, Humid
Hot summers and cold winters with high humidity. Significant heating and cooling loads. This climate zone encompasses parts of Virginia, Kentucky, Missouri, Kansas, Maryland, Delaware, New Jersey and includes major cities like Richmond, Louisville, Kansas City, St. Louis.
Common Questions About Zone 4A
Zone 4A definition
This page explains what IECC climate zone 4A means in HVAC and building-code terms.
Cities in zone 4A
Use the city examples below to answer common lookup searches for this zone.
Heating and cooling profile
See whether zone 4A 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 4A Means
Temperature class
Mixed (Zone 4)
Moisture class
Moist (A)
Load priority
Heating-dominant
Quick definition
Hot summers and cold winters with high humidity. Significant heating and cooling loads.
Common City Lookups for Zone 4A
| City | IECC zone answer | Why it matters |
|---|---|---|
| Richmond | Richmond is commonly treated as IECC climate zone 4A in this guide. | High heating and cooling loads |
| Louisville | Louisville is commonly treated as IECC climate zone 4A in this guide. | High heating and cooling loads |
| Kansas City | Kansas City is commonly treated as IECC climate zone 4A in this guide. | High heating and cooling loads |
| St. Louis | St. Louis is commonly treated as IECC climate zone 4A in this guide. | High heating and cooling loads |
| Baltimore | Baltimore is commonly treated as IECC climate zone 4A in this guide. | High heating and 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
- •High heating and cooling loads
- •Humidity control year-round
- •Seasonal system changeover
- •Freeze protection
- •Mold and moisture management
Common Equipment
- ✓Heat pumps with backup heat
- ✓Gas furnaces with AC
- ✓Dual-fuel systems
- ✓Central dehumidification
Energy Code Requirements
Equipment Efficiency
- ⚠SEER 13+ minimum
- ⚠HSPF 7.7+ for heat pumps
- ⚠AFUE 80+ for furnaces
- ⚠Duct testing requirements
Insulation Requirements
Major Cities in Zone 4A
Quick Reference
Calculate Load
Use our load calculators with the design temperatures and requirements specific to Zone 4A.