Boundary noise limits and where a condenser sits in them
An operator who receives a complaint about a condenser usually reaches for a quieter unit or a service visit. Neither answers the question the rules ask, which is what the level reads at the affected boundary and against which limit. Money spent before that is spent blind.
By Team Snowflake | Updated 6 Aug 2026
The measuring point, not the loudness of the machine
Noise from plant is regulated at the edge of the premises it stands on. Not at the machine, and not in the room where it is a problem. That one choice of measuring point is what separates a noise complaint from a compliance question, and it is the fact most operators miss before they start pricing a fix.
NEA's technical guideline for air-conditioning and mechanical ventilation systems states the measuring points plainly. Equipment standing at ground level is read at the site boundary. Equipment above ground level, on a roof for instance, is read close to the source at the same height, and the level is then computed for a point on the site boundary at that height. Where a noise barrier has been built, the reading is taken behind it, at its mid-height.
Distance, screening and height therefore sit between the machine and the number that counts. A loud machine deep inside a large site can read lower at the line than a quiet one bolted to the edge of a small one. Sound figures printed in a brochure describe the machine under test conditions. They describe nothing about your line.
Two adjustments push the assessment further away from raw loudness. The guideline sets a background noise correction, which compares the permitted level against the background and adds a correction where the two sit close together. It also sets modifying-factor penalties for sound that carries a particular character: a clear tone, heavy low-frequency content, impulsive knocks, or a level that keeps falling back to background and rising again. Each of those adds a penalty, subject to a stated cap.
The character rule is the one operators find backwards. A machine that is not especially loud, but hums on a single note, can be assessed more harshly than a louder machine producing even, broadband sound. What the noise is like carries weight of its own.
| What moves the boundary reading | Which direction it moves | What to establish first |
|---|---|---|
| What moves the boundary readingDistance from the plant to the property line | Which direction it movesMore distance, lower reading | What to establish firstWhere the line actually runs, from the plan |
| What moves the boundary readingA wall, recess or narrow shaft beside the plant | Which direction it movesReflections push it up | What to establish firstWhether the machine sits open or boxed in |
| What moves the boundary readingHeight, for plant standing on a roof | Which direction it movesAssessed at the line at the same height | What to establish firstWhich neighbouring floor the plant is level with |
| What moves the boundary readingA barrier already screening the plant | Which direction it movesLowers it, and moves where the reading is taken | What to establish firstWhether anything screens the machine today |
| What moves the boundary readingA tone, a knock, or a level that keeps dropping out | Which direction it movesAdds a penalty on top of the measured level | What to establish firstWhat the sound is like, not only how loud |
Who is next door, and what time it is
There is no single figure to comply with. Limits are written against the type of premises being affected, not against the type of machine making the noise. NEA's guideline sorts affected premises into noise-sensitive uses, residential uses, and everything else, with the tightest figures attached to the noise-sensitive group.
Each of those groups then carries separate figures for a daytime band, an evening band and a night band, and the night figures are the tightest of all. Nothing about the machine changes between one band and the next. That is why the same condenser can sit inside the limit through a working afternoon and outside it once the block has gone to bed.
Mixed-use neighbours default to the stricter treatment. Where the affected development holds both commercial and residential use, the guideline says the more stringent residential limits should apply. A tower with shops below and flats above is read as flats.
Land next door counts even when nothing has been built on it yet. The guideline sends qualified persons to the URA master plan to check the intended use of adjacent premises, and tells them to apply the stricter limit where current and intended uses differ. An empty plot zoned for housing is treated as the neighbour it is going to become. That matters before siting plant along a line that today faces a car park.
The figures themselves are deliberately absent from this page. They vary between instruments, they are set out per premises type and per period, and they are amended from time to time. Take them from NEA for the premises you actually occupy, rather than from any article, this one included.
Which regime covers your premises?
Three separate instruments carry the phrase boundary noise, and they do not reach the same premises. Picking the wrong one is how an operator ends up arguing against a limit that was never aimed at them.
Construction sites sit under their own regulations, written for work that is temporary and loud by nature. Factory premises sit under the boundary noise limits regulations made for factory premises. The definition NEA uses covers premises used for industrial or manufacturing purposes, and takes in repair and processing workshops and warehouses, while excluding construction sites. A workshop or a warehouse falls inside it. A shop, an office or a restaurant does not.
Cooling and ventilation plant in non-industrial buildings is addressed by a technical guideline, not by those regulations. The guideline defines a non-industrial building as one used for trade, business or commerce. It names shopping complexes, office towers, hotels, schools and hospitals. It leaves out factory and residential premises. The guideline is written for qualified persons to apply at specification, design and installation stage. NEA also lists it among the pollution control requirements a new development should be designed to meet.
Read together, the practical shape appears. For most commercial premises the boundary figure was a design target, meant to be hit at building-plan stage. It was not a test an occupier gets put through later. Two questions matter once a complaint does arrive: whether the plant has drifted from what the design assumed, and whether anything about the neighbour has changed.
| Where the plant stands | What addresses its noise | What that means when a complaint lands |
|---|---|---|
| Where the plant standsA working construction site | What addresses its noiseIts own construction noise regulations | What that means when a complaint landsA temporary regime, separate from permanent plant |
| Where the plant standsA workshop, factory or warehouse | What addresses its noiseBoundary noise limits regulations for factory premises | What that means when a complaint landsA measured limit at the line, by neighbour and period |
| Where the plant standsAn office tower, hotel, school or shopping complex | What addresses its noiseA technical guideline for cooling and ventilation plant | What that means when a complaint landsA design target set at building-plan stage |
| Where the plant standsA licensed food premises | What addresses its noiseThat guideline, plus licence conditions and good practice | What that means when a complaint landsConditions can be enforced without a decibel figure |
| Where the plant standsA flat or a landed home | What addresses its noiseNeither regime. Residential is the protected party | What that means when a complaint landsA neighbour dispute route, and by-laws under strata |
Licence conditions bite before a decibel figure does
Licensed premises carry a second lever with no connection to the boundary tables. NEA publishes a good practice guide for foodshops. It asks operators to keep apparatus and equipment in good working condition, so that it does not cause a noise nuisance to nearby residential or commercial premises. It asks for silencers or suitable attenuators on aircon compressors or exhaust systems where required. It also notes that the relevant authorities may require an owner or occupier to engage a noise consultant.
For a shop or an F&B operator, that is usually the live risk. A condition attached to a licence can be raised, and acted on, without anyone producing a measured figure at a property line. The wider set of cooling risks worth clearing before an outlet opens is covered separately.
A home condenser is not a boundary noise case
A household unit sits outside all three instruments. It is not a factory premises, and residential premises are excluded from the guideline's own definition of a non-industrial building. Residential appears across these instruments as the party being protected, not as the source being measured.
So a neighbour upset about a flat's condenser is in a neighbour dispute, not a compliance matter, and that runs through a different route entirely: community mediation first, and the Community Disputes Resolution Tribunals if it does not settle. In a strata development the by-laws held by the management corporation are a separate lever again, and often a quicker one. What that body is, and what it can require, has its own page. The household experience of a unit that is only a problem after dark belongs with the night-noise page rather than here.
What usually makes a condenser the one that gets named
Most complaints trace back to siting, mounting or the hour of operation. Very few trace back to somebody buying a loud model.
Plant hemmed in by hard surfaces reads higher than the same plant in the open. A recess, a narrow gap between two blocks, or a wall sitting directly behind the discharge sends sound back out rather than letting it spread and fall away. The machine has not changed. The path to the property line has. Two identical installations on one estate can draw a complaint at one address and silence at the other, purely on that.
Mounting is the case where a quieter machine changes nothing at all. Where feet sit hard on a slab, or a bracket is bolted through a shared wall, part of the vibration travels through the structure rather than the air. It surfaces as a hum inside a room with no view of the plant whatsoever. Anti-vibration mounts, and the state they are in, decide how much crosses over. A neighbour describing a hum in the wall rather than a noise outside the window is describing that path.
Night turns a tolerable machine into a complaint for two reasons at once. The permitted level drops after the evening band, and the background level around the plant drops with it. The machine holds its output while everything around it goes quiet, so it stands further above background at exactly the point where less is allowed. The guideline also applies its intermittent-noise penalty at night only.
A fourth cause is drift rather than design. Fouled coils make the fan and compressor work harder, bearings develop play, guards and brackets work loose, and rubber mounts harden with heat and age. Each of those raises output, or adds a character the machine did not have at commissioning. That is the case where a service visit genuinely is the answer, which is reason enough to rule it in or out before anyone re-sites anything.
What to establish before spending anything
Four things decide whether a quote is worth reading. Where the property line runs and what sits across it. Which instrument, if any, reaches your premises. What the level reads at that line during the hours the complaint names, with the background recorded alongside it. And whether the sound carries a character that attracts a penalty.
The measurement only counts if the instrument does. The guideline calls for a calibrated integrating sound level meter meeting the international standards for the top instrument class. A phone app is a useful private hint about whether the noise gets worse once the estate quietens. It is not evidence, and nobody assessing the complaint will treat a phone reading as proof.
If a contractor proposes a replacement condenser on the strength of a quieter number in a brochure, push back. That number comes from a test chamber at a fixed distance. It says nothing about reflections off the wall behind your unit, nothing about vibration entering the bracket, and nothing about where your line sits. Ask what the proposed machine is expected to read at the boundary, and on what basis.
The order of fixes follows the diagnosis, not the price list. Structure-borne transfer calls for isolation and mounting work, and a new machine is beside the point. An airborne path out of a boxed-in position calls for screening or a change of position. A level that has drifted upward from a healthy baseline calls for the machine to be serviced back to it. Choosing before measuring is how an operator pays twice.
Related ground sits on separate pages. Where an outdoor unit is physically allowed to go is a placement question. What a newly commissioned system should and should not sound like belongs with post-installation noise. What a particular sound says about the machine is a diagnostic matter covered elsewhere.
The figures behind all of this belong to NEA, and its published version is the only one worth quoting. This page sets out the shape of the framework so that the right question gets asked first. Treat it as orientation, not as legal advice, and read the current text of whichever instrument covers the premises you occupy. Where a lease, a licence condition or a set of by-laws sets something stricter, the stricter one is what has to be met.
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.