Seattle, WA Noise from Specific Sources: HVAC & Mechanical Noise (2026)

King County Code Chapter 12.86 applies to residential mechanical equipment under WAC 173-60. Heat pumps and AC condensers must meet 55 dBA daytime and 45 dBA nighttime limits at the adjacent property line. Modern variable-speed heat pumps typically operate at 40-55 dBA at 3 feet, meaning setback or acoustic shielding is often required near property lines to meet the 45 dBA night limit. King County Department of Local Services permit review includes mechanical setbacks, and the 2021 International Residential Code as adopted in Washington requires minimum 3-foot setbacks from property lines for outdoor condensing units. Common mitigation includes sound blankets, louvered enclosures, and positioning away from shared boundaries. KCC 21A.22.080 requires mechanical equipment to meet state energy code but does not impose additional noise limits beyond KCC 12.86. Pool and spa heaters are subject to the same standards. Complaints are handled through King County Code Enforcement with potential acoustical measurement for chronic issues.