Wisconsin Climate Zones by County
Wisconsin's 72 counties span climate zones 5A to 6A under the 2021 International Energy Conservation Code (IECC). Zone 6A is the most common, with 42 of the 72. For reference, Milwaukee and Madison are in zone 5A and Green Bay is in 6A.
Insulation minimums for each zone in Wisconsin
| Zone | Counties | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|---|
| 5A | 30 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
| 6A | 42 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
Minimums from the 2021 IECC (Table R402.1.3). Many areas still enforce an older edition, so check with your local building department. See sources.
Which energy code Wisconsin uses
Wisconsin enforces the 2009 IECC with amendments for homes (in effect since Jan 2016). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments. See every state's energy code.
What changed from the 2018 map
45 counties moved one zone warmer in the 2021 map: Adams County (6 → 5), Ashland County (7 → 6), Bayfield County (7 → 6), Burnett County (7 → 6), Calumet County (6 → 5), Columbia County (6 → 5), Crawford County (6 → 5), Dane County (6 → 5), Dodge County (6 → 5), Douglas County (7 → 6), Florence County (7 → 6), Fond du Lac County (6 → 5), and 33 more marked in the table below. If your town still enforces the 2018 or 2015 code, the older zone applies to permits.
Every county in Wisconsin
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Adams County | 5A | 6A changed | Insulation → |
| Ashland County | 6A | 7 changed | Insulation → |
| Barron County | 6A | 6A | Insulation → |
| Bayfield County | 6A | 7 changed | Insulation → |
| Brown County | 6A | 6A | Insulation → |
| Buffalo County | 6A | 6A | Insulation → |
| Burnett County | 6A | 7 changed | Insulation → |
| Calumet County | 5A | 6A changed | Insulation → |
| Chippewa County | 6A | 6A | Insulation → |
| Clark County | 6A | 6A | Insulation → |
| Columbia County | 5A | 6A changed | Insulation → |
| Crawford County | 5A | 6A changed | Insulation → |
| Dane County | 5A | 6A changed | Insulation → |
| Dodge County | 5A | 6A changed | Insulation → |
| Door County | 6A | 6A | Insulation → |
| Douglas County | 6A | 7 changed | Insulation → |
| Dunn County | 6A | 6A | Insulation → |
| Eau Claire County | 6A | 6A | Insulation → |
| Florence County | 6A | 7 changed | Insulation → |
| Fond du Lac County | 5A | 6A changed | Insulation → |
| Forest County | 6A | 7 changed | Insulation → |
| Grant County | 5A | 6A changed | Insulation → |
| Green County | 5A | 6A changed | Insulation → |
| Green Lake County | 5A | 6A changed | Insulation → |
| Iowa County | 5A | 6A changed | Insulation → |
| Iron County | 6A | 7 changed | Insulation → |
| Jackson County | 6A | 6A | Insulation → |
| Jefferson County | 5A | 6A changed | Insulation → |
| Juneau County | 5A | 6A changed | Insulation → |
| Kenosha County | 5A | 6A changed | Insulation → |
| Kewaunee County | 6A | 6A | Insulation → |
| La Crosse County | 5A | 6A changed | Insulation → |
| Lafayette County | 5A | 6A changed | Insulation → |
| Langlade County | 6A | 7 changed | Insulation → |
| Lincoln County | 6A | 7 changed | Insulation → |
| Manitowoc County | 6A | 6A | Insulation → |
| Marathon County | 6A | 6A | Insulation → |
| Marinette County | 6A | 6A | Insulation → |
| Marquette County | 6A | 6A | Insulation → |
| Menominee County | 6A | 6A | Insulation → |
| Milwaukee County | 5A | 6A changed | Insulation → |
| Monroe County | 5A | 6A changed | Insulation → |
| Oconto County | 6A | 6A | Insulation → |
| Oneida County | 6A | 7 changed | Insulation → |
| Outagamie County | 5A | 6A changed | Insulation → |
| Ozaukee County | 5A | 6A changed | Insulation → |
| Pepin County | 6A | 6A | Insulation → |
| Pierce County | 6A | 6A | Insulation → |
| Polk County | 6A | 6A | Insulation → |
| Portage County | 6A | 6A | Insulation → |
| Price County | 6A | 7 changed | Insulation → |
| Racine County | 5A | 6A changed | Insulation → |
| Richland County | 5A | 6A changed | Insulation → |
| Rock County | 5A | 6A changed | Insulation → |
| Rusk County | 6A | 6A | Insulation → |
| Sauk County | 5A | 6A changed | Insulation → |
| Sawyer County | 6A | 7 changed | Insulation → |
| Shawano County | 6A | 6A | Insulation → |
| Sheboygan County | 6A | 6A | Insulation → |
| St. Croix County | 6A | 6A | Insulation → |
| Taylor County | 6A | 7 changed | Insulation → |
| Trempealeau County | 6A | 6A | Insulation → |
| Vernon County | 5A | 6A changed | Insulation → |
| Vilas County | 6A | 7 changed | Insulation → |
| Walworth County | 5A | 6A changed | Insulation → |
| Washburn County | 6A | 7 changed | Insulation → |
| Washington County | 5A | 6A changed | Insulation → |
| Waukesha County | 5A | 6A changed | Insulation → |
| Waupaca County | 6A | 6A | Insulation → |
| Waushara County | 5A | 6A changed | Insulation → |
| Winnebago County | 5A | 6A changed | Insulation → |
| Wood County | 6A | 6A | Insulation → |
Source: Pacific Northwest National Laboratory, Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (2022).
Frequently asked questions
What climate zone is Wisconsin?
Wisconsin spans IECC climate zones 5A to 6A; zone 6A is the most common. Find your county in the table above, or search by ZIP code.
How much attic insulation do I need in Wisconsin?
The 2021 IECC calls for R-60 in the attic everywhere in Wisconsin.
What energy code does Wisconsin use?
Wisconsin enforces the 2009 IECC with amendments for homes (in effect since Jan 2016). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
More for Wisconsin: Last frost dates in Wisconsin · Wisconsin planting zones · Frost line depth by state