IECC climate zone 7 on the US map (very cold climate)

What this diagram shows

A simplified map of the United States with IECC climate zone 7 highlighted. Climate zone 7 is a very cold climate covering northern Minnesota, far-northern Maine, and high-elevation mountain areas. A legend names every zone from warm zone 1 in the south to cold zone 8 in the north; the colder the zone, the higher the insulation R-value the code requires. The figure lists example cities in zone 7 and the IECC minimum R-values for the attic, walls, and floor.