IECC Climate Zone Window Guides
Expert window selection guides for all 8 IECC climate zones. Find detailed recommendations, energy requirements, and cost analysis for your specific climate.
How to Find Your Climate Zone
Method 1: Check the IECC Climate Zone Map (PNNL/DOE official map)
Method 2: Search for your city in our city guides - each page shows the climate zone
Method 3: Ask your building department - they enforce local energy codes based on climate zone
Note: Some areas have subcategories (A = humid, B = dry, C = marine). The letter doesn't affect basic window requirements, but impacts moisture management strategies.
Browse by Climate Zone
Hot-Humid Climate Windows
Hot-Humid (Tropical/Subtropical)
U-Factor Max
U-0.50 (insulation less critical)
SHGC
SHGC ≤0.25 (REQUIRED - blocks ...
Primary Concern: Cooling costs and solar heat gain
3 city guides available
Warm Climate Windows
Warm (Hot-Dry and Warm-Humid)
U-Factor Max
U-0.40
SHGC
SHGC ≤0.25 (REQUIRED for cooli...
Primary Concern: Cooling costs dominate (60-70% of energy bill)
3 city guides available
Mixed Climate Windows
Mixed (Marine and Mixed-Humid)
U-Factor Max
U-0.32
SHGC
No specific SHGC requirement (...
Primary Concern: Balanced heating and cooling needs
5 city guides available
Cold Climate Windows
Cold (Cold-Dry and Cold-Humid)
U-Factor Max
U-0.32
SHGC
No requirement (but 0.35-0.45 ...
Primary Concern: Heating costs dominate (70-75% of energy bill)
6 city guides available
Very Cold Climate Windows
Very Cold (Cold-Dry and Cold-Humid)
U-Factor Max
U-0.30 (stricter than Zone 5)
SHGC
No requirement (0.35-0.50 reco...
Primary Concern: Extreme heating costs (80%+ of energy bill)
7 city guides available
Extremely Cold Climate Windows
Extremely Cold (Subarctic/Severe Continental)
U-Factor Max
U-0.27 (STRICTEST US requirement)
SHGC
No requirement (maximize solar...
Primary Concern: Catastrophic heating costs without premium windows
4 city guides available
Subarctic Climate Windows
Subarctic/Arctic
U-Factor Max
U-0.27 or better (Zone 8 same as Zone 7)
SHGC
No requirement (maximize passi...
Primary Concern: Survival-level heating requirements
Quick Climate Zone Comparison
| Zone | Climate Type | U-Factor Max | Recommended |
|---|---|---|---|
| Zone 1-2 | Hot-Humid | U-0.50 (insulation less critical) | Double-pane with advanced coating |
| Zone 3 | Warm | U-0.40 | Double-pane with spectrally selective coating |
| Zone 4 | Mixed | U-0.32 | Triple-pane (recommended for marine climates) |
| Zone 5 | Cold | U-0.32 | Triple-pane |
| Zone 6 | Very Cold | U-0.30 (stricter than Zone 5) | Triple-pane with krypton or quad-pane |
| Zone 7 | Extremely Cold | U-0.27 (STRICTEST US requirement) | Quad-pane |
| Zone 8 | Subarctic | U-0.27 or better (Zone 8 same as Zone 7) | Quad-pane or vacuum glazing |