IECC 2021 climate zone
Climate zone 7: very cold
Northern Minnesota and Wisconsin, the high Rockies and parts of Alaska.
Zone 7 covers 68 counties in 7 states, home to about 1,687,910 people (FEMA NRI population). ENERGY STAR’s target for an uninsulated attic here is R60; with 3–4 inches already in place, add to R49.
Insulation targets for zone 7
| Where | Guidance |
|---|---|
| Attic, uninsulated | R60 |
| Attic, 3–4 inches already | R49 |
| Floor over unheated space | R38 |
| Walls | When siding is removed: blow insulation into empty cavities and add R5 to R10 insulative sheathing; on an insulated 2x4 wall, add R10 sheathing. |
| Basement or crawlspace walls | Add R15 insulative wall sheathing or an R19 batt. |
Homeowner retrofit guidance, not your local code. Your jurisdiction may enforce an older or amended IECC; ask the building department before a permit job.
What it means for upkeep
Most zone 7 counties fall in the very cold Building America region. Long, hard winters: pipes, heating equipment and roof snow load drive the plan.
Largest counties in zone 7
Anchorage Municipality, AK290,985St. Louis County, MN200,067Matanuska-Susitna Borough, AK107,000Grand Forks County, ND73,042Ward County, ND69,879Aroostook County, ME67,034Crow Wing County, MN66,020Marquette County, MI65,947Kenai Peninsula Borough, AK58,731Beltrami County, MN46,103Itasca County, MN45,006Carlton County, MN36,175Polk County, MN31,153Summit County, CO31,040Cass County, MN30,036Pine County, MN28,831Routt County, CO24,767Teton County, WY23,250Hubbard County, MN21,321Lincoln County, WY19,576Bethel Census Area, AK18,633Park County, CO17,300Pitkin County, CO17,292Gunnison County, CO16,897Grand County, CO15,695Aitkin County, MN15,674Roseau County, MN15,292Wadena County, MN14,054Pennington County, MN13,900Rolette County, ND12,180Koochiching County, MN12,059Ramsey County, ND11,577Rio Grande County, CO11,498Lake County, MN10,884Walsh County, ND10,553Clear Creek County, CO9,391Marshall County, MN9,012Sublette County, WY8,723Clearwater County, MN8,512Lake County, CO7,405Pembina County, ND6,825Norman County, MN6,420Bottineau County, ND6,379Benson County, ND5,945Cook County, MN5,590Mahnomen County, MN5,404McHenry County, ND5,344Aleutians West Census Area, AK5,168Dillingham Census Area, AK4,845Kittson County, MN4,201Pierce County, ND3,976Red Lake County, MN3,934Lake of the Woods County, MN3,752Cavalier County, ND3,703Aleutians East Borough, AK3,374Nelson County, ND3,007Renville County, ND2,282Burke County, ND2,201Divide County, ND2,195Towner County, ND2,161
States in this zone: Minnesota (23), North Dakota (16), Colorado (13), Alaska (10), Wyoming (3), Michigan (2), Maine (1).
PNNL county zone fileFEMA NRI population