Seattle’s heat pump noise ordinance sets a sound limit at the property line, not a setback distance. Between two houses, the noise code allows 55 dBA during the day and 45 dBA at night. For heat pumps, SDCI adds a noise review for any outdoor unit in a side yard: a predicted property-line level of 47 dBA or less on the heating rating passes, and anything louder needs a fix.
The Seattle Heat Pump Company plans ducted heat pump projects across Seattle and King County, with the outdoor unit sited to meet these limits, and the work is carried out by licensed and insured contractors. This guide covers how the limit is measured, why side yards get the attention, which fixes work, and where the persistent “30-foot setback” claim comes from.
Key takeaways
- Seattle's residential limits are 55 dBA by day and 45 dBA at night at the property line.
- Night runs 10pm to 7am on weekdays and 10pm to 9am on weekends and holidays.
- Side-yard units get an SDCI noise review; a predicted 47 dBA or less on the heating rating passes.
- There is no fixed 30-foot setback for heat pump noise in Seattle.
The limits and the hours
Seattle’s noise code sets sound limits based on the zones of the source and the receiving property. For one house next to another, the limit at the property line is 55 dBA during the day and 45 dBA at night. Nighttime runs from 10pm to 7am on weekdays and from 10pm to 9am on weekends and holidays.
The nighttime figure is the one that matters for a heat pump, because a heat pump runs at night all winter. A cold, damp January night in the 30s is when the compressor and fan work hardest, so the design has to meet 45 dBA under heating conditions, not just on a mild afternoon.
dBA is a logarithmic scale weighted toward the frequencies people hear best. Every 10 dB increase sounds roughly twice as loud, and in open air the level from a single source drops by about 6 dB each time the distance doubles. Hard surfaces such as a house wall or a fence a few feet away reflect sound and reduce that drop, which is part of why a narrow side yard is the difficult case.
Why side yards trigger a review
SDCI’s guidance is direct: equipment in a side yard needs a noise review as part of the permit, and front and rear yards are the recommended locations. The reasoning is geometric. SDCI’s guidance names minimum side yards of 3 feet as the typical problem. Where a house sits that close to the line, a unit in the gap is only a few feet from the neighbor’s property, often between two walls that bounce its sound back and forth.
The review predicts the sound level at the property line from the unit’s published heating sound rating and its distance to the line, with adjustments for nearby reflecting surfaces. If the prediction comes in at 47 dBA or less, the location passes. If not, the design changes before the permit is approved, which is far cheaper than changing it after a complaint.
Noise review is part of the refrigeration permit process. The Seattle permit guide covers that permit and the rest of the inspections. SDCI’s guidance also notes that the user agreements sometimes available for cooling-only equipment are not available for heat pumps.
Options when a location is too loud
When the first-choice location does not pass, there are four practical fixes, often combined.
| Fix | How it works | Tradeoffs |
|---|---|---|
| Quieter model | Variable-speed outdoor units often have lower sound ratings, especially at reduced speed | The rating at the heating condition is what counts; compare like with like |
| Compressor blanket | An acoustic wrap around the compressor inside the cabinet absorbs some of its noise | Must be a manufacturer-approved part so it does not trap heat |
| Sound barrier | A solid, sound-rated screen between the unit and the property line blocks the direct path | Needs clearance for airflow and service; a lattice or open fence does little |
| Relocation | Move the unit to the rear or front yard, or farther from the line | Longer refrigerant line runs and sometimes a different route into the house |
Mounting matters too, though the noise review does not model it. A unit on an isolated pad or a properly specified wall bracket transmits less vibration into the house and the ground. A unit bolted rigidly to a wall can hum through the framing. Fan and compressor faults that develop later can also raise sound levels, so a unit that suddenly gets louder is worth a service call. The variable-speed versus single-stage guide explains why inverter units tend to be quieter at the low speeds where they spend most of a Seattle winter.
Site the outdoor unit before you choose itThe assessment looks at your lot, the property lines and the route into the house.
Get an EstimateThe 30-foot setback myth
One Seattle homeowner posted that their installer said code required a heat pump to sit 30 feet from the property line, and asked whether that could be real. It is not. Seattle’s rule is a sound level at the property line. No fixed distance applies to heat pump noise. On a lot with 3-foot side yards, a 30-foot rule would leave no legal place for the unit at all, which is a good sign the rule does not exist.
The claim probably grows out of a real constraint stated badly. A loud unit may need considerable distance to drop below 45 dBA, and an installer who carries only one or two models may find that none of them passes in a tight side yard. Other homeowners report being told that only one unit on the market would meet the limit for their location. That may have been true for the models the installer sold, but the answer to a noise problem is a calculation with the actual sound rating, not a rule of thumb.
If you hear a setback figure, ask where it comes from. A zoning setback for structures is a different rule from the noise code, and Bellevue’s equipment-placement rule for new homes, below, is a real but separate requirement.
Bellevue’s rules
Bellevue applies the same residential noise limits as Seattle: 55 dBA by day and 45 dBA at night at the property line. It enforces them on complaint rather than at permit inspection, so the burden is on getting the siting right before installation.
Bellevue’s zoning code adds a placement rule for new homes and additions larger than 1,000 square feet: mechanical equipment goes in the rear yard, at least 5 feet from the property line, and side-yard installations need sound screening. That rule is the real source of some setback confusion on the Eastside. For an existing house replacing a furnace, the mechanical permit and the noise limits are the main requirements. See heat pumps in Bellevue for the rest of the local picture, including PSE’s rates and what they mean in the operating cost guide.
Replacing an existing outdoor unit
A replacement heat pump needs a refrigeration permit just as a new one does, so a unit in a side yard should expect the same noise review. That can work in your favor. An older single-speed unit that sits in a side yard today may be louder than a current variable-speed model, and the replacement is the moment to check whether the existing spot passes or whether a better one exists. The refrigerant change since January 1, 2026 often means a new indoor coil and a look at the line set anyway, so moving the outdoor unit can add less work than it would on its own. The heat pump replacement page covers what else a replacement involves.
What to ask about noise before you sign
Three questions settle most noise issues on a quote. Where exactly will the outdoor unit sit, and how far is that from the nearest property line? What is the model’s heating sound rating, from the manufacturer’s data? And if the location is a side yard, has the noise review been predicted, and what fix is included if it comes in above 47 dBA? A bidder who can answer all three has thought about the permit. One who cannot may be planning to find out at inspection. The Seattle heat pump guide puts noise alongside the other decisions in a project.
Siting on a narrow Seattle lot
On a tight city lot, the outdoor unit location is often the first design decision, not the last. A rear yard near the corner of the house usually clears the limit easily and keeps the line set short. A front-yard location can work where the rear yard is inaccessible, with attention to appearance and clearances. The side yard is possible when the numbers work, and the review exists to check them.
Location also affects the rest of the job: the line set route into a basement or crawlspace, where the condensate drains, and access for service. Where a lot is narrow and the house fills most of its width, as on some lots in Ballard or Wallingford and Green Lake, these tradeoffs get decided early. The installation process guide shows where siting fits into the sequence, the how a heat pump works guide explains what the outdoor unit contains, and the ducted heat pump installation assessment includes the siting check. When comparing bids, the quote comparison guide suggests asking each bidder where the unit will go and whether a noise review is expected.