Climate ZonesVirginiaFairfax

Fairfax, Virginia HVAC Climate Zone

Fairfax is located in IECC Climate Zone 4A (Mixed - Humid). Get accurate Manual J load calculations with official design temperatures for Fairfax.

Climate Zone
4A
Winter Design
13°F
Summer Design
91°F
ZIP Codes
5

Fairfax HVAC Contractors: Get Your Free Manual J Report

Climate Zone 4A requires precise load calculations. Upload your Fairfax blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with Fairfax's exact design temperatures (13°F winter / 91°F summer).

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Verify Your Fairfax ZIP Code

Enter your ZIP code to confirm it's in Fairfax and get climate zone details.

Fairfax covers 5 ZIP codes: 22030, 22031, 22032, 22033, 22034

Fairfax Design Temperatures

Official ASHRAE design temperatures for Fairfax, used for accurate Manual J load calculations.

Winter 99% Design Temp
13°F
Summer 1% Design Temp
91°F
Summer Wet Bulb
75°F

IECC Requirements for Zone 4A

Minimum insulation and window requirements for Fairfax per IECC 2021.

Wall Insulation:R-20
Roof/Ceiling:R-49
Floor Insulation:R-19
Window U-Factor:0.32
Window SHGC:0.4

Energy Code: 2021 IECC

Recommended HVAC Equipment for Fairfax

Heating Systems

Gas furnace (90%+ AFUE)
Heat pump
Typical AFUE
92-96%

Cooling Systems

AC (14-16 SEER)
Heat pump
Typical SEER
14-16 SEER

Related Climate Zone Pages

Learn More About
Climate Zone 4A
View All Zones in
Virginia
HVAC Permits for
Fairfax, Virginia

Get Free Manual J Calculations for Fairfax

Upload your Fairfax blueprint and get a professional Manual J load calculation using official Zone 4A design temperatures. First report is FREE.

Fairfax design temps
Zone 4A compliant
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