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

Two Land Use Code sections address residential HVAC noise, and the Issaquah code cross-references them to each other. LUC 18.508.030(D), under the general standards for accessory structures and amenities, sets the working numbers: heat pumps, air conditioner condensers, and similar mechanical equipment located on single-family and townhome lots must not exceed 55 dbA during the day and 45 dbA at night as measured at the property line. The section calls this a State-adopted standard.

If the standard cannot be met, the units shall provide all of the following mitigation measures. First, the unit is placed farthest from the neighboring properties as practically feasible. Second, a fencing or vegetation buffer serves as a noise barrier when practically feasible. Third, quieter components, such as a sound blanket or quieter fans, are installed onto the mechanical equipment. The word all matters: the three measures are cumulative, not a menu.

LUC 18.518.020(D) adds an exemption. Heat pumps, air conditioner condensers, and similar mechanical equipment on single-family and townhome style developments are exempt from the limits adopted from Chapter 173-60 WAC in subsection A, provided the maximum dbA from the units does not exceed 73dbA or the units meet Air-Conditioning, Heating, and Refrigeration Institute (AHRI) standard 270. That subsection ends by directing the reader to IMC 18.508.030(D) for additional standards. The code does not spell out how the 55 and 45 dbA figures and the 73dbA exemption interact, so a homeowner or installer should treat the property-line figures and the mitigation list as the Land Use Code's own text and confirm the unit's rated dbA or AHRI 270 status before installation.

Equipment of any kind is also covered by LUC 18.518.020(B): manufacturer's specifications can be required by the Community Planning and Development Department before the building permit issues, and verification of compliance can be required after construction but before a certificate of occupancy.