Washington County is in IECC Climate Zone 6A (Cold - Humid). Get accurate Manual J load calculations with official ASHRAE design temperatures for Washington County.
Washington County, Vermont is classified under IECC Climate Zone 6A (Cold - Humid), a heating-dominated region with humid moisture conditions. With 30 ZIP codes and 1 communities, every HVAC installation in Washington County must use the ASHRAE design temperatures of -11°F (99% winter heating) and 86°F (1% summer cooling) for accurate Manual J load calculations.
As a heating-dominated zone, Washington 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 -11°F design conditions.
Minimum insulation R-values and window performance for Climate Zone 6A in Washington County, VT.
| 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 Washington County blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with Washington County's exact design temperatures (-11°F winter / 86°F summer).
Enter your ZIP code to confirm it's in Washington County and get climate zone details.
Official ASHRAE design temperatures for Washington County, VT, used for accurate Manual J load calculations.
Minimum insulation and window requirements for Washington 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 Washington County share Climate Zone 6A requirements.
Compare climate zones with other counties in Vermont. Different zones require different HVAC equipment sizing.
Upload your Washington County blueprint and get a professional Manual J load calculation using official Zone 6A design temperatures. First report is FREE.
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