St. Louis Climate Zone & Energy Code

Climate Zone: IECC Climate Zone 4A (mixed-humid). St. Louis's river valley location produces hot, humid summers (95°F/76°F cooling design) and cold winters (6°F heating design) with the Mississippi and Missouri Rivers amplifying both summer humidity and winter cold fronts.

Energy Code & Manual J Requirement: Missouri has no mandatory statewide residential energy code. St. Louis County and many municipalities enforce voluntarily adopted IECC versions requiring Manual J. Confirm requirements with the specific AHJ for each project.

Local Electric Utility: Ameren Missouri

Building Department: City of St. Louis Building Division

Local Trade Association: ACCA Missouri / ASHRAE Missouri Chapter / SMACNA Heartland