IECC Climate Zones for HVAC Design
IECC climate zones are the foundation of HVAC load calculations and building energy code compliance in the United States. Each zone has specific design temperature ranges, insulation requirements, and HVAC system recommendations.
Zone 1 — Very Hot
Summer °F: 88–95°F | Winter °F: 40–55°F
Typical Cities: Miami, FL, Honolulu, HI
Zone 2 — Hot
Summer °F: 90–110°F | Winter °F: 24–38°F
Typical Cities: Houston, TX, Phoenix, AZ
Zone 3 — Warm
Summer °F: 88–100°F | Winter °F: 16–32°F
Typical Cities: Atlanta, GA, Dallas, TX
Zone 4 — Mixed
Summer °F: 84–95°F | Winter °F: 6–22°F
Typical Cities: New York, NY, Washington, DC
Zone 5 — Cool
Summer °F: 80–92°F | Winter °F: -4–14°F
Typical Cities: Chicago, IL, Boston, MA
Zone 6 — Cold
Summer °F: 78–90°F | Winter °F: -12–2°F
Typical Cities: Minneapolis, MN, Burlington, VT
Zone 7 — Very Cold
Summer °F: 74–86°F | Winter °F: -30–-8°F
Typical Cities: Fairbanks, AK, Duluth, MN
Zone 8 — Subarctic
Summer °F: 68–80°F | Winter °F: -50–-20°F
Typical Cities: Utqiaġvik (Barrow), AK, Deadhorse, AK