Colorado climate zones
Colorado’s 64 counties fall in 4 IECC 2021 climate zones: 4B (5), 5B (34), 6B (12), 7 (13).
Zone 4B: mixed-dry
Attic target R60 (ENERGY STAR)Baca County (Mixed-dry) · Bent County (Mixed-dry) · Las Animas County (Mixed-dry) · Otero County (Mixed-dry) · Prowers County (Mixed-dry)
Zone 5B: cool-dry
Attic target R60 (ENERGY STAR)Adams County (Cold) · Arapahoe County (Cold) · Boulder County (Cold) · Broomfield County (Cold) · Cheyenne County (Cold) · Crowley County (Cold) · Custer County (Cold) · Delta County (Cold) · Denver County (Cold) · Douglas County (Cold) · El Paso County (Cold) · Elbert County (Cold) · Fremont County (Cold) · Garfield County (Cold) · Gilpin County (Cold) · Huerfano County (Cold) · Jefferson County (Cold) · Kiowa County (Cold) · Kit Carson County (Cold) · La Plata County (Cold) · Larimer County (Cold) · Lincoln County (Cold) · Logan County (Cold) · Mesa County (Cold) · Montezuma County (Cold) · Montrose County (Cold) · Morgan County (Cold) · Phillips County (Cold) · Pueblo County (Cold) · Sedgwick County (Cold) · Teller County (Cold) · Washington County (Cold) · Weld County (Cold) · Yuma County (Cold)
Zone 6B: cold-dry
Attic target R60 (ENERGY STAR)Alamosa County (Cold) · Archuleta County (Cold) · Chaffee County (Cold) · Conejos County (Cold) · Costilla County (Cold) · Dolores County (Cold) · Eagle County (Cold) · Moffat County (Cold) · Ouray County (Cold) · Rio Blanco County (Cold) · Saguache County (Cold) · San Miguel County (Cold)
Zone 7: very cold
Attic target R60 (ENERGY STAR)Clear Creek County (Very cold) · Grand County (Very cold) · Gunnison County (Very cold) · Hinsdale County (Very cold) · Jackson County (Very cold) · Lake County (Very cold) · Mineral County (Very cold) · Park County (Very cold) · Pitkin County (Very cold) · Rio Grande County (Very cold) · Routt County (Very cold) · San Juan County (Very cold) · Summit County (Very cold)