Climate Zone 12 — the Sacramento Valley and foothills band that runs up the I-5 / I-80 corridor between Stockton and Chico — is one of the hotter-summer zones in the state, and the 2025 Energy Code asks more of cooling performance there than the 2022 cycle did. We've tightened our Title 24 baseline for CZ12 so projects clear compliance comfortably rather than scraping the line. If your project is in CZ12, the verification already uses these values — there's nothing you need to change on a project we've run. This note is for the design side, so the windows and equipment you spec match what compliance expects.

What to spec in Climate Zone 12

  • Windows: solar-heat-gain coefficient (SHGC) of 0.18 or lower. This is the single most important change. Lower-SHGC glass keeps summer sun from overheating the home, which is what the code is protecting against in this zone.
  • Cooling: a high-efficiency system (SEER2 22 / EER2 16 or better). The peak-cooling number (EER2) is the one that matters most here — it measures performance on the hottest design days, which is exactly when CZ12 homes are under load.
  • Heating: a quality heat pump (HSPF2 9.0 or better). Most major-brand inverter-driven heat pumps meet this; older single-stage units generally don't.

Where it matters on the plans

  • Put the low-SHGC requirement on the west, southwest, and south faces first — those are the sun-exposed elevations driving the cooling load. In practice it's simplest to spec the same glass on every face rather than split the window schedule across two products.
  • Call the efficiency tier on the schedule, not a specific model. Listing "SEER2 ≥ 22 / EER2 ≥ 16" lets the contractor choose any qualifying unit. Pinning a single model number on the drawings is what creates substitution headaches at procurement.
  • A 19-SEER2 unit that passed in the 2022 cycle won't carry CZ12 anymore. If a contractor pushes back on the higher tier, the mid-range inverter-driven catalog from the major brands meets it without an exotic premium.

A note on the High-Performance design option

In CZ12, our Balanced option is usually the better fit than High-Performance for projects that want a clean, simple wall assembly. The High-Performance envelope's thinner wall leaves less cooling headroom in this hot zone, so for most CZ12 designs we steer toward Balanced — which keeps the standard wall plus the upgraded heating, cooling, and water-heating equipment. You'll see this reflected automatically in the options we present for a CZ12 project; if simplicity was the goal, Balanced gets you there with more margin to spare.

The short version

If you're designing into CZ12: low-SHGC windows (≤ 0.18), an efficient heat-pump system (SEER2 ≥ 22 / EER2 ≥ 16, HSPF2 ≥ 9.0), and let us handle the compliance math. The earlier you lock the window and equipment schedules to these numbers, the smoother plan check goes.