Climate zones
Climate Zone 6
Climate zone 6 is the IECC's "cold" zone. Under the 2021 map it covers 423 counties in 18 states, including Minneapolis, Burlington VT, Fargo and Bozeman. By moisture: 6A (humid) 304 and 6B (dry) 119. Zone 6 has long, cold winters. The requirements match zone 5 for attics and walls, with heavier mass-wall insulation.
Insulation minimums in zone 6 (2021 IECC)
| Part of the house | 6A, 6B |
|---|---|
| Attic / ceiling | R-60 |
| Wood-frame walls | R-30, or 20+5ci, or 13+10ci, or R-20ci |
| Mass walls (block, brick) | R-15 exterior / R-20 interior |
| Floors over unheated space | R-30 |
| Basement walls | R-15ci, or R-19, or 13+5ci |
| Slab edge | R-10, 4 ft deep |
| Crawl space walls | R-15ci, or R-19, or 13+5ci |
| Windows: max U-factor | U-0.30 |
| Windows: max SHGC | No requirement |
"13+5ci" means R-13 between the studs plus R-5 foam board over the outside. Minimums from 2021 IECC Table R402.1.3; many areas still enforce an older edition, so check with your building department.
Existing home? ENERGY STAR recommends R-60 in an uninsulated attic, or adding R-49 if you already have 3–4 inches. The climate zone lookup works out how many inches to add for your county.
States in climate zone 6
| State | Counties in zone 6 | Subzones |
|---|---|---|
| Minnesota | 61 of 87 | 6A |
| Montana | all 56 | 6B |
| South Dakota | 48 of 66 | 6A |
| Michigan | 44 of 83 | 6A |
| Wisconsin | 42 of 72 | 6A |
| North Dakota | 37 of 53 | 6A |
| Idaho | 22 of 44 | 6B |
| New York | 18 of 62 | 6A |
| Wyoming | 17 of 23 | 6B |
| Iowa | 15 of 99 | 6A |
| Maine | 15 of 16 | 6A |
| Vermont | all 14 | 6A |
| Colorado | 12 of 64 | 6B |
| Utah | 7 of 29 | 6B |
| Alaska | 5 of 27 | 6A |
| New Hampshire | 5 of 10 | 6A |
| Washington | 3 of 39 | 6B |
| California | 2 of 58 | 6B |
Every county in zone 6
Open a state to see its counties. The state pages list every county's zone, including the ones in other zones.
Minnesota (61)
- Anoka County (6A)
- Becker County (6A)
- Benton County (6A)
- Big Stone County (6A)
- Blue Earth County (6A)
- Brown County (6A)
- Carver County (6A)
- Chippewa County (6A)
- Chisago County (6A)
- Clay County (6A)
- Cottonwood County (6A)
- Dakota County (6A)
- Dodge County (6A)
- Douglas County (6A)
- Faribault County (6A)
- Freeborn County (6A)
- Goodhue County (6A)
- Grant County (6A)
- Hennepin County (6A)
- Isanti County (6A)
- Jackson County (6A)
- Kanabec County (6A)
- Kandiyohi County (6A)
- Lac qui Parle County (6A)
- Le Sueur County (6A)
- Lincoln County (6A)
- Lyon County (6A)
- Martin County (6A)
- McLeod County (6A)
- Meeker County (6A)
- Mille Lacs County (6A)
- Morrison County (6A)
- Mower County (6A)
- Murray County (6A)
- Nicollet County (6A)
- Nobles County (6A)
- Olmsted County (6A)
- Otter Tail County (6A)
- Pipestone County (6A)
- Pope County (6A)
- Ramsey County (6A)
- Redwood County (6A)
- Renville County (6A)
- Rice County (6A)
- Rock County (6A)
- Scott County (6A)
- Sherburne County (6A)
- Sibley County (6A)
- Stearns County (6A)
- Steele County (6A)
- Stevens County (6A)
- Swift County (6A)
- Todd County (6A)
- Traverse County (6A)
- Wabasha County (6A)
- Waseca County (6A)
- Washington County (6A)
- Watonwan County (6A)
- Wilkin County (6A)
- Wright County (6A)
- Yellow Medicine County (6A)
Montana (56)
- Beaverhead County (6B)
- Big Horn County (6B)
- Blaine County (6B)
- Broadwater County (6B)
- Carbon County (6B)
- Carter County (6B)
- Cascade County (6B)
- Chouteau County (6B)
- Custer County (6B)
- Daniels County (6B)
- Dawson County (6B)
- Deer Lodge County (6B)
- Fallon County (6B)
- Fergus County (6B)
- Flathead County (6B)
- Gallatin County (6B)
- Garfield County (6B)
- Glacier County (6B)
- Golden Valley County (6B)
- Granite County (6B)
- Hill County (6B)
- Jefferson County (6B)
- Judith Basin County (6B)
- Lake County (6B)
- Lewis and Clark County (6B)
- Liberty County (6B)
- Lincoln County (6B)
- Madison County (6B)
- McCone County (6B)
- Meagher County (6B)
- Mineral County (6B)
- Missoula County (6B)
- Musselshell County (6B)
- Park County (6B)
- Petroleum County (6B)
- Phillips County (6B)
- Pondera County (6B)
- Powder River County (6B)
- Powell County (6B)
- Prairie County (6B)
- Ravalli County (6B)
- Richland County (6B)
- Roosevelt County (6B)
- Rosebud County (6B)
- Sanders County (6B)
- Sheridan County (6B)
- Silver Bow County (6B)
- Stillwater County (6B)
- Sweet Grass County (6B)
- Teton County (6B)
- Toole County (6B)
- Treasure County (6B)
- Valley County (6B)
- Wheatland County (6B)
- Wibaux County (6B)
- Yellowstone County (6B)
South Dakota (48)
- Aurora County (6A)
- Beadle County (6A)
- Brookings County (6A)
- Brown County (6A)
- Buffalo County (6A)
- Butte County (6A)
- Campbell County (6A)
- Clark County (6A)
- Codington County (6A)
- Corson County (6A)
- Custer County (6A)
- Davison County (6A)
- Day County (6A)
- Deuel County (6A)
- Dewey County (6A)
- Edmunds County (6A)
- Fall River County (6A)
- Faulk County (6A)
- Grant County (6A)
- Hamlin County (6A)
- Hand County (6A)
- Hanson County (6A)
- Harding County (6A)
- Hughes County (6A)
- Hyde County (6A)
- Jerauld County (6A)
- Kingsbury County (6A)
- Lake County (6A)
- Lawrence County (6A)
- Lincoln County (6A)
- Marshall County (6A)
- McCook County (6A)
- McPherson County (6A)
- Meade County (6A)
- Miner County (6A)
- Minnehaha County (6A)
- Moody County (6A)
- Pennington County (6A)
- Perkins County (6A)
- Potter County (6A)
- Roberts County (6A)
- Sanborn County (6A)
- Shannon County (6A)
- Spink County (6A)
- Sully County (6A)
- Turner County (6A)
- Walworth County (6A)
- Ziebach County (6A)
Michigan (44)
- Alcona County (6A)
- Alger County (6A)
- Alpena County (6A)
- Antrim County (6A)
- Arenac County (6A)
- Baraga County (6A)
- Benzie County (6A)
- Charlevoix County (6A)
- Cheboygan County (6A)
- Chippewa County (6A)
- Clare County (6A)
- Crawford County (6A)
- Delta County (6A)
- Dickinson County (6A)
- Emmet County (6A)
- Gladwin County (6A)
- Gogebic County (6A)
- Grand Traverse County (6A)
- Houghton County (6A)
- Iosco County (6A)
- Iron County (6A)
- Isabella County (6A)
- Kalkaska County (6A)
- Lake County (6A)
- Leelanau County (6A)
- Luce County (6A)
- Mackinac County (6A)
- Manistee County (6A)
- Mason County (6A)
- Mecosta County (6A)
- Menominee County (6A)
- Missaukee County (6A)
- Montmorency County (6A)
- Newaygo County (6A)
- Oceana County (6A)
- Ogemaw County (6A)
- Ontonagon County (6A)
- Osceola County (6A)
- Oscoda County (6A)
- Otsego County (6A)
- Presque Isle County (6A)
- Roscommon County (6A)
- Schoolcraft County (6A)
- Wexford County (6A)
Wisconsin (42)
- Ashland County (6A)
- Barron County (6A)
- Bayfield County (6A)
- Brown County (6A)
- Buffalo County (6A)
- Burnett County (6A)
- Chippewa County (6A)
- Clark County (6A)
- Door County (6A)
- Douglas County (6A)
- Dunn County (6A)
- Eau Claire County (6A)
- Florence County (6A)
- Forest County (6A)
- Iron County (6A)
- Jackson County (6A)
- Kewaunee County (6A)
- Langlade County (6A)
- Lincoln County (6A)
- Manitowoc County (6A)
- Marathon County (6A)
- Marinette County (6A)
- Marquette County (6A)
- Menominee County (6A)
- Oconto County (6A)
- Oneida County (6A)
- Pepin County (6A)
- Pierce County (6A)
- Polk County (6A)
- Portage County (6A)
- Price County (6A)
- Rusk County (6A)
- Sawyer County (6A)
- Shawano County (6A)
- Sheboygan County (6A)
- St. Croix County (6A)
- Taylor County (6A)
- Trempealeau County (6A)
- Vilas County (6A)
- Washburn County (6A)
- Waupaca County (6A)
- Wood County (6A)
North Dakota (37)
- Adams County (6A)
- Barnes County (6A)
- Billings County (6A)
- Bowman County (6A)
- Burleigh County (6A)
- Cass County (6A)
- Dickey County (6A)
- Dunn County (6A)
- Eddy County (6A)
- Emmons County (6A)
- Foster County (6A)
- Golden Valley County (6A)
- Grant County (6A)
- Griggs County (6A)
- Hettinger County (6A)
- Kidder County (6A)
- LaMoure County (6A)
- Logan County (6A)
- McIntosh County (6A)
- McKenzie County (6A)
- McLean County (6A)
- Mercer County (6A)
- Morton County (6A)
- Mountrail County (6A)
- Oliver County (6A)
- Ransom County (6A)
- Richland County (6A)
- Sargent County (6A)
- Sheridan County (6A)
- Sioux County (6A)
- Slope County (6A)
- Stark County (6A)
- Steele County (6A)
- Stutsman County (6A)
- Traill County (6A)
- Wells County (6A)
- Williams County (6A)
Idaho (22)
- Adams County (6B)
- Bannock County (6B)
- Bear Lake County (6B)
- Bingham County (6B)
- Blaine County (6B)
- Boise County (6B)
- Bonner County (6B)
- Bonneville County (6B)
- Boundary County (6B)
- Butte County (6B)
- Camas County (6B)
- Caribou County (6B)
- Clark County (6B)
- Custer County (6B)
- Franklin County (6B)
- Fremont County (6B)
- Jefferson County (6B)
- Lemhi County (6B)
- Madison County (6B)
- Oneida County (6B)
- Teton County (6B)
- Valley County (6B)
New York (18)
- Chenango County (6A)
- Clinton County (6A)
- Delaware County (6A)
- Essex County (6A)
- Franklin County (6A)
- Fulton County (6A)
- Hamilton County (6A)
- Herkimer County (6A)
- Jefferson County (6A)
- Lewis County (6A)
- Madison County (6A)
- Montgomery County (6A)
- Oneida County (6A)
- Otsego County (6A)
- St. Lawrence County (6A)
- Sullivan County (6A)
- Ulster County (6A)
- Warren County (6A)
Wyoming (17)
- Albany County (6B)
- Big Horn County (6B)
- Campbell County (6B)
- Carbon County (6B)
- Converse County (6B)
- Crook County (6B)
- Fremont County (6B)
- Hot Springs County (6B)
- Johnson County (6B)
- Natrona County (6B)
- Niobrara County (6B)
- Park County (6B)
- Sheridan County (6B)
- Sweetwater County (6B)
- Uinta County (6B)
- Washakie County (6B)
- Weston County (6B)
Iowa (15)
- Black Hawk County (6A)
- Cerro Gordo County (6A)
- Clay County (6A)
- Dickinson County (6A)
- Emmet County (6A)
- Hancock County (6A)
- Kossuth County (6A)
- Lyon County (6A)
- Mitchell County (6A)
- O'Brien County (6A)
- Osceola County (6A)
- Palo Alto County (6A)
- Sioux County (6A)
- Winnebago County (6A)
- Worth County (6A)
Maine (15)
- Androscoggin County (6A)
- Cumberland County (6A)
- Franklin County (6A)
- Hancock County (6A)
- Kennebec County (6A)
- Knox County (6A)
- Lincoln County (6A)
- Oxford County (6A)
- Penobscot County (6A)
- Piscataquis County (6A)
- Sagadahoc County (6A)
- Somerset County (6A)
- Waldo County (6A)
- Washington County (6A)
- York County (6A)
Vermont (14)
- Addison County (6A)
- Bennington County (6A)
- Caledonia County (6A)
- Chittenden County (6A)
- Essex County (6A)
- Franklin County (6A)
- Grand Isle County (6A)
- Lamoille County (6A)
- Orange County (6A)
- Orleans County (6A)
- Rutland County (6A)
- Washington County (6A)
- Windham County (6A)
- Windsor County (6A)
Colorado (12)
- Alamosa County (6B)
- Archuleta County (6B)
- Chaffee County (6B)
- Conejos County (6B)
- Costilla County (6B)
- Dolores County (6B)
- Eagle County (6B)
- Moffat County (6B)
- Ouray County (6B)
- Rio Blanco County (6B)
- Saguache County (6B)
- San Miguel County (6B)
Utah (7)
- Daggett County (6B)
- Duchesne County (6B)
- Morgan County (6B)
- Rich County (6B)
- Summit County (6B)
- Uintah County (6B)
- Wasatch County (6B)
Alaska (5)
- Haines (6A)
- Juneau (6A)
- Kodiak Island (6A)
- Skagway-Hoonah-Angoon Census Area (6A)
- Wrangell-Petersburg Census Area (6A)
New Hampshire (5)
- Belknap County (6A)
- Carroll County (6A)
- Coos County (6A)
- Grafton County (6A)
- Sullivan County (6A)
Washington (3)
- Ferry County (6B)
- Pend Oreille County (6B)
- Stevens County (6B)
California (2)
- Alpine County (6B)
- Mono County (6B)
What changed in the 2021 map
50 of these counties moved here from zone 7 in the 2021 map. The 2021 code redrew the map with newer weather data; across the US, most counties that changed moved one zone warmer. If your town still enforces the 2018 or an older code, the old zone applies to permits.
Frequently asked questions
What is climate zone 6?
One of the eight US climate zones in the International Energy Conservation Code (IECC). Zone 6 has long, cold winters. The requirements match zone 5 for attics and walls, with heavier mass-wall insulation. It covers 423 counties in 18 states.
How much attic insulation do I need in climate zone 6?
In zone 6, the 2021 IECC calls for R-60 in the attic of a new home. For an existing home, ENERGY STAR recommends R-60 in an uninsulated attic, or adding R-49 if you already have 3–4 inches.
Which states are in climate zone 6?
Minnesota, Montana, South Dakota, Michigan, Wisconsin, North Dakota, Idaho, New York, Wyoming, Iowa, Maine, Vermont, Colorado, Utah, Alaska, New Hampshire, Washington and California. Montana and Vermont are entirely in zone 6.
What do the letters A and B mean?
They describe moisture: 6A is humid and 6B is dry. In zone 6 the insulation minimums in the table above are the same for every letter.
Sources: Pacific Northwest National Laboratory, Guide to Determining Climate Zone by County (2022); 2021 IECC Table R402.1.3; ENERGY STAR. See how we calculate.