IECC climate zone 8 on the US map (subarctic climate)

What this diagram shows

A simplified map of the United States with IECC climate zone 8 highlighted. Climate zone 8 is a subarctic climate covering interior Alaska. 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 8 and the IECC minimum R-values for the attic, walls, and floor.