Great Falls Climate Zone & Energy Code

Climate Zone: IECC Climate Zone 7 (very cold). Great Falls's high plains north-central Montana position produces extreme winter cold (-20°F heating design) with exposure to Arctic air masses and chinook wind events that produce rapid temperature swings.

Energy Code & Manual J Requirement: Montana Residential Building Code (IECC 2021). ACCA Manual J required for Cascade County HVAC permits. IECC Climate Zone 7 requires particularly high envelope performance standards.

Local Electric Utility: NorthWestern Energy

Building Department: City of Great Falls Building Department

Local Trade Association: PHCC Montana