San Diego attics need R-30 to R-38 in new homes and R-49 when an inland, mountain or desert attic is altered, depending on climate zone 7, 10, 14 or 15. Coastal zone 7 upgrades only require R-19, but ENERGY STAR recommends R-38 to R-49.
The most effective way to lower a San Diego energy bill in 2026 is to fix the building envelope first (Title 24-compliant windows, attic insulation, duct sealing), replace an aging air conditioner with a SEER2 heat pump, then shift remaining usage away from SDG&E's 4-9 p.m. peak using a smart thermostat, shading, and appliance timing.
For San Diego homes in 2026, casement and fixed picture windows rank as the most energy-efficient types, followed by sliding and double-hung, because their tighter seals and compression locks meet Title 24's 0.30 U-factor and 0.23 SHGC thresholds most easily with standard Low-E dual-pane glass. No triple-pane upgrade is required for code compliance.
