Seattle Climate Zone & Energy Code
Climate Zone: IECC Climate Zone 4C (marine). Seattle's Puget Sound location produces one of the mildest climates in the US: 21°F heating design and 83°F/66°F cooling design. Heat pumps are extremely efficient here and now dominant in the market.
Energy Code & Manual J Requirement: Washington State Energy Code (WSEC) — one of the most progressive in the US. Strong heat pump requirements. ACCA Manual J required for all King County HVAC permit applications.
Local Electric Utility: Seattle City Light (City-owned utility)
Building Department: City of Seattle Dept. of Construction & Inspections (SDCI)
Local Trade Association: ACCA Northwest Chapter / ASHRAE Pacific Northwest Chapter / SMACNA Western Washington