Climate ZonesWashingtonCowlitz

Cowlitz, Washington HVAC Climate Zone

Cowlitz is located in IECC Climate Zone 4C (Mixed - Marine). Get accurate Manual J load calculations with official design temperatures for Cowlitz.

Climate Zone
4C
Winter Design
29°F
Summer Design
85°F
ZIP Codes
10

Cowlitz HVAC Contractors: Get Your Free Manual J Report

Climate Zone 4C requires precise load calculations. Upload your Cowlitz blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with Cowlitz's exact design temperatures (29°F winter / 85°F summer).

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Verify Your Cowlitz ZIP Code

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

Cowlitz covers 10 ZIP codes: 98581, 98603, 98611, 98616, 98625, 98626, 98632, 98645, 98649, 98674

Cowlitz Design Temperatures

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

Winter 99% Design Temp
29°F
Summer 1% Design Temp
85°F
Summer Wet Bulb
67°F

IECC Requirements for Zone 4C

Minimum insulation and window requirements for Cowlitz 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 Cowlitz

Heating Systems

Gas furnace
Heat pump
Typical AFUE
92-95%

Cooling Systems

AC (optional)
Heat pump
Typical SEER
14 SEER

Related Climate Zone Pages

Learn More About
Climate Zone 4C
View All Zones in
Washington
HVAC Permits for
Cowlitz, Washington

Get Free Manual J Calculations for Cowlitz

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Cowlitz design temps
Zone 4C compliant
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