St. Louis is in IECC Climate Zone 7 (Very Cold). Get accurate Manual J load calculations with official design temperatures for St. Louis.
St. Louis, Minnesota falls within IECC Climate Zone 7 (Very Cold), a heating-dominated region with moist moisture conditions. HVAC contractors working in St. Louis must use the official ASHRAE design temperatures of -18°F (99% winter) and 87°F (1% summer) when performing Manual J load calculations. These values represent the outdoor conditions your heating and cooling system must handle 99% and 1% of the year, respectively — ensuring proper equipment sizing without costly over- or under-sizing.
Because Zone 7 is heating-dominated, insulation levels are critical. St. Louis homes require a minimum of R-20 wall insulation, R-60 ceiling insulation, and windows with a U-factor of 0.3 or lower per the IECC 2021 energy code.
Minimum insulation R-values and window performance requirements for Climate Zone 7 in St. Louis, Minnesota.
| Building Component | Minimum Requirement | Unit |
|---|---|---|
| Ceiling / Attic Insulation | R-60 | R-value |
| Wall Insulation | R-20 | R-value |
| Floor Insulation | R-38 | R-value |
| Window U-Factor | 0.3 | BTU/hr-ft²-°F |
| Window SHGC | 0.45 | Coefficient |
| Air Infiltration | 0.15 | ACH50 |
Climate Zone 7 requires precise load calculations. Upload your St. Louis blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with St. Louis's exact design temperatures (-18°F winter / 87°F summer).
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Official ASHRAE design temperatures for St. Louis, used for accurate Manual J load calculations.
Minimum insulation and window requirements for St. Louis per IECC 2021.
Energy Code: 2020 IECC
Upload your St. Louis blueprint and get a professional Manual J load calculation using official Zone 7 design temperatures. First report is FREE.
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