HVAC Climate Zones Guide
The United States is divided into 8 climate zones based on heating and cooling degree days. Each zone has specific design requirements for HVAC systems, building codes, and energy efficiency standards. Understanding your climate zone is essential for accurate load calculations and proper equipment selection.
Temperature Zones (1-8)
Moisture Levels (A, B, C)
Example: Zone 3A means "Warm and Moist" - typical of southeastern states like Georgia and North Carolina. Zone 2B means "Hot and Dry" - common in southwestern desert regions like Arizona and Nevada.
All Climate Zones
Zone 1A
VeryVery hot summers with high humidity year-round. Minimal heating requirements.
Zone 1B
VeryVery hot summers with low humidity. Extreme temperature swings between day and night.
Zone 2A
HotHot summers with high humidity. Mild winters requiring some heating.
Zone 2B
HotHot summers with low humidity. Moderate heating needs with large temperature swings.
Zone 3A
WarmWarm summers with humidity. Moderate heating and cooling needs throughout the year.
Zone 3B
WarmWarm summers with low humidity. Cool winters requiring moderate heating.
Zone 3C
WarmMild temperatures year-round with marine influence. Limited heating and cooling needs.
Zone 4A
MixedHot summers and cold winters with high humidity. Significant heating and cooling loads.
Zone 4B
MixedHot summers and cold winters with low humidity. Large temperature variations.
Zone 4C
MixedMild temperatures with marine influence. Moderate heating needs, minimal cooling.
Zone 5A
CoolWarm summers and cold winters with humidity. Heating loads dominate.
Zone 5B
CoolWarm summers and cold winters with low humidity. High heating loads.
Zone 6A
ColdShort warm summers and long cold winters. Very high heating loads.
Zone 6B
ColdShort warm summers and long cold winters with low humidity.
Zone 7
VeryShort cool summers and very long cold winters. Heating loads dominate completely.
Zone 8
SubarcticCool summers and extremely cold winters. Heating only climate.
Why Climate Zones Matter for HVAC Design
Equipment Selection
Different climate zones require different equipment types and efficiencies. Heat pumps work well in Zone 3-4, but may need backup heat in Zone 5+. Cooling equipment sizing varies dramatically from Zone 1 to Zone 8.
- • Heat pump vs. furnace decisions
- • Efficiency requirements (SEER, HSPF)
- • Equipment sizing factors
- • Backup heating needs
Building Codes
Each climate zone has specific insulation requirements, window performance standards, and air sealing requirements. These directly affect heating and cooling loads and must be factored into calculations.
- • Insulation R-values
- • Window U-factors and SHGC
- • Air sealing requirements
- • Duct insulation standards
Load Calculations
Climate zone determines design temperatures, heating/cooling degree days, and humidity levels used in load calculations. These factors directly impact equipment sizing and energy consumption estimates.
- • Design temperature selection
- • Humidity load calculations
- • Solar gain factors
- • Infiltration rates