IECC Climate Zone 7 — Very Cold

Updated Mar 26, 2026

Severe cold climate covering Alaska interior, far northern Minnesota/Wisconsin/Maine. Extreme heating loads. Highest insulation and air sealing requirements. Triple-pane windows often justified.

TAGS

IECC very-cold Alaska subarctic extreme

DETAILS

hdd range

8,000-9,000

iecc zone

air tightness

3 ACH50 max

example cities

Fairbanks AK, International Falls MN

roof insulation

R-60

wall insulation

R-20+R-10ci or R-13+R-15ci

SOURCES

🔗https://codes.iccsafe.org/content/IECC2021P1

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