St. Croix County is in IECC Climate Zone 6A (Cold - Humid). Get accurate Manual J load calculations with official ASHRAE design temperatures for St. Croix County.
St. Croix County, Wisconsin is classified under IECC Climate Zone 6A (Cold - Humid), a heating-dominated region with humid moisture conditions. With 11 ZIP codes and 1 communities, every HVAC installation in St. Croix County must use the ASHRAE design temperatures of -9°F (99% winter heating) and 89°F (1% summer cooling) for accurate Manual J load calculations.
As a heating-dominated zone, St. Croix County requires robust insulation — a minimum of R-20 in walls, R-49 in ceilings, and R-30 in floors. Windows must meet a U-factor of 0.3 or lower. These requirements ensure homes maintain comfort during the coldest -9°F design conditions.
Minimum insulation R-values and window performance for Climate Zone 6A in St. Croix County, WI.
| Building Component | Minimum Requirement | Unit |
|---|---|---|
| Ceiling / Attic Insulation | R-49 | R-value |
| Wall Insulation | R-20 | R-value |
| Floor Insulation | R-30 | R-value |
| Window U-Factor | 0.3 | BTU/hr-ft²-°F |
| Window SHGC | 0.4 | Coefficient |
| Air Infiltration | 0.15 | ACH50 |
Climate Zone 6A requires precise load calculations. Upload your St. Croix County blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with St. Croix County's exact design temperatures (-9°F winter / 89°F summer).
Enter your ZIP code to confirm it's in St. Croix County and get climate zone details.
Official ASHRAE design temperatures for St. Croix County, WI, used for accurate Manual J load calculations.
Minimum insulation and window requirements for St. Croix County per IECC 2021 energy code.
Climate Zone 6A: Cold - Humid - Cold climate with very cold winters and warm summers. Very high heating loads, moderate cooling needs.
1 cities and communities in St. Croix County share Climate Zone 6A requirements.
Compare climate zones with other counties in Wisconsin. Different zones require different HVAC equipment sizing.
Upload your St. Croix County blueprint and get a professional Manual J load calculation using official Zone 6A design temperatures. First report is FREE.
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