Climate ZonesVirginiaLoudoun

Loudoun, Virginia HVAC Climate Zone

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

Climate Zone
4A
Winter Design
13°F
Summer Design
91°F
ZIP Codes
17

Loudoun HVAC Contractors: Get Your Free Manual J Report

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

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Verify Your Loudoun ZIP Code

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

Loudoun covers 17 ZIP codes: 20105, 20117, 20118, 20129, 20132, 20141, 20147, 20148, 20152, 20158 and 7 more

Loudoun Design Temperatures

Official ASHRAE design temperatures for Loudoun, 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 Loudoun 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 Loudoun

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
Loudoun, Virginia

Get Free Manual J Calculations for Loudoun

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Loudoun design temps
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