San Luis Obispo County is in IECC Climate Zone 3C (Warm - Marine). Get accurate Manual J load calculations with official ASHRAE design temperatures for San Luis Obispo County.
San Luis Obispo County, California is classified under IECC Climate Zone 3C (Warm - Marine), a mixed-climate region with marine moisture conditions. With 35 ZIP codes and 1 communities, every HVAC installation in San Luis Obispo County must use the ASHRAE design temperatures of 23°F (99% winter heating) and 99°F (1% summer cooling) for accurate Manual J load calculations.
With balanced heating and cooling loads, San Luis Obispo County homes require well-rounded insulation — R-20 walls, R-30 ceilings, R-19 floors — and windows with both U-factor 0.32 and SHGC 0.4 to handle both winter lows and summer highs.
Minimum insulation R-values and window performance for Climate Zone 3C in San Luis Obispo County, CA.
| Building Component | Minimum Requirement | Unit |
|---|---|---|
| Ceiling / Attic Insulation | R-30 | R-value |
| Wall Insulation | R-20 | R-value |
| Floor Insulation | R-19 | R-value |
| Window U-Factor | 0.32 | BTU/hr-ft²-°F |
| Window SHGC | 0.4 | Coefficient |
| Air Infiltration | 0.15 | ACH50 |
Climate Zone 3C requires precise load calculations. Upload your San Luis Obispo County blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with San Luis Obispo County's exact design temperatures (23°F winter / 99°F summer).
Enter your ZIP code to confirm it's in San Luis Obispo County and get climate zone details.
Official ASHRAE design temperatures for San Luis Obispo County, CA, used for accurate Manual J load calculations.
Minimum insulation and window requirements for San Luis Obispo County per IECC 2021 energy code.
Climate Zone 3C: Warm - Marine - Mild, marine climate with cool summers and mild winters. Moderate heating needs, minimal cooling.
1 cities and communities in San Luis Obispo County share Climate Zone 3C requirements.
Compare climate zones with other counties in California. Different zones require different HVAC equipment sizing.
Upload your San Luis Obispo County blueprint and get a professional Manual J load calculation using official Zone 3C design temperatures. First report is FREE.
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