Noise from a neighbour's heat pump or air conditioner: what are your rights and solutions?
More and more people complain about the humming noise of a neighbour's heat pump or air conditioner. In a VRT NWS report, Filip Verbandt, chairman of the Belgian Acoustical Association, confirms that the problem occurs in all densely populated areas and that installers are often insufficiently informed. On this page you will find in one place: what the Flemish Code of good practice says, what rights you have as an affected neighbour, and which acoustic solutions Noise Solutions uses to bring the noise durably below the standard.
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Why a heat pump or air conditioner causes nuisance
An outdoor unit consists of a compressor and a fan. The compressor produces a low, pure hum, which acousticians call "tonal noise". As Filip Verbandt puts it in the VRT NWS article on heat pump noise: it will not make you deaf, but it can lead to stress and sleep problems. Precisely because a hum is perceived by the human ear as particularly annoying, Flemish regulation applies an extra penalty during the official measurement.
How heat pump noise works: Lw, Lp and dB(A)
To understand a measurement by an acoustic expert or the municipality, it helps to distinguish two concepts. The sound power level (Lw) is a fixed property of the unit, like the power of a lamp. The sound pressure level (Lp) is what is measured at a specific location, and is influenced by distance, facades, reflection and background noise. Both are expressed in dB, but because the human ear perceives low and high frequencies differently, the value is corrected to dB(A). A difference of only 3 dB(A) is barely audible to the ear, but doubles the sound energy and can be decisive for meeting the standard or not.
- Manufacturers publish the Lw value of their heat pumps and air conditioners in the European Commission's EPREL database (eprel.ec.europa.eu), useful for comparing your neighbour's unit with quieter alternatives
- For an audible hum, a tonal penalty of +5 dB is added to the measurement, in line with the Code of good practice
- An official measurement is taken at the plot boundary at 1.5 m height, and at the openable windows of your home
Distance and surroundings: why your facade can worsen the problem
The same heat pump can be completely inaudible for one neighbour and disturb another's sleep. This is because sound pressure depends heavily on distance and on what sits between source and ear. A simple rule of thumb from the Flemish Code of good practice: every doubling of the distance between the unit and the listener reduces the sound pressure by roughly 6 dB(A). Reflection, however, can cancel out that advantage.
- A smooth facade, a glass sliding window or a metal canopy acts as a mirror for noise and can raise the perceived pressure by several dB
- A unit placed in a corner or recess between two facades sounds louder than a freestanding unit at the same distance
- Vegetation, rough finishes, grass and gravel absorb a small part of the noise, the effect is limited (1 to 2 dB) but mainly prevents noise from concentrating in one direction
- Open ventilation grilles in your windows form a noise leak through which the hum enters the bedroom directly, even when the facade otherwise appears well sealed
The noise standard for heat pumps and air conditioners in Flanders
The Code of good practice of the Flemish Department of Environment (September 2024) sets clear limit values at the plot boundary, measured at 1.5 metres height. If this value is exceeded, the owner is required to take measures.
- Daytime (7am to 10pm): maximum 45 dB(A) at the plot boundary
- Night-time (10pm to 7am): maximum 40 dB(A), so 5 dB stricter
- Tonal penalty: +5 dB for an audible hum. A unit measuring 42 dB is then assessed as 47 dB and exceeds the daytime standard
- Noise is also measured at the openable windows of neighbouring homes
Your rights as an affected neighbour
If you are bothered by a neighbour's heat pump or air conditioner, follow these steps. A friendly conversation with the neighbour is always the first step. If that does not help, you can rely on Flemish regulation.
- Talk to the neighbour, ask whether the quiet night mode is activated and whether the unit stands on vibration dampers
- Request an official noise measurement from the municipality or environmental inspection at the plot boundary and at your window
- If 45 dB(A) is exceeded during the day or 40 dB(A) at night, the owner is required to take acoustic measures
- Consider requesting an independent acoustic analysis, which we can also provide
The order of solutions according to the Code of good practice
The Code puts forward a clear ladder of measures. A full enclosure is deliberately the last step, since it can restrict the unit's ventilation and lead to faults if executed incorrectly. In most cases a correctly placed acoustic screen is enough.
- 1. Address the source: quiet night mode, correct sizing, free air circulation
- 2. Vibration isolation: dampers and a base that approaches at least the weight of the unit
- 3. Acoustic screening: a soundwall between the unit and the plot boundary, often 4 to 8 m²
- 4. Absorbing panels: capture reflections against facades and in recesses
- 5. Full enclosure with forced ventilation: last resort
What an acoustic screen typically achieves
A well dimensioned acoustic screen between the unit and your plot usually reduces the sound pressure by 10 to 20 dB(A). For reference: a reduction of 10 dB(A) is perceived by the ear as a halving of the noise. In almost all cases this is enough to bring a unit exceeding the standard back within the Flemish limits, without affecting the operation of the heat pump. The price of such a screen starts at approximately 200 EUR per m² including installation (excluding VAT). The full approach and products are described on our page on heat pump enclosures.
We come to measure and propose a tailored solution
Every situation is different: the type of unit, the distance to the plot boundary, the facades and background noise together determine the right solution. Our experts visit free of charge anywhere in Belgium and Luxembourg, assess your situation against the Code of good practice, and propose the most cost-efficient solution. Request a no-obligation acoustic analysis.
More technical background can be found in our guide how does an acoustic wall work. For the commercial product page and standard solutions, see heat pump and air conditioner enclosures.
Sources: VRT NWS report featuring Filip Verbandt, chairman of the Belgian Acoustical Association (31 March 2026). Code of good practice for managing noise nuisance from heat pumps and air conditioning units, Flemish Department of Environment, September 2024.
Frequently asked questions about heat pump or air conditioner noise
My neighbour's heat pump makes a humming noise. What are my rights?+
The Flemish Code of good practice regards a typical heat pump hum as tonal noise. As a result, a penalty of +5 dB is applied during the official measurement. A unit producing 42 dB is then assessed as 47 dB, exceeding the daytime standard of 45 dB. You can request a noise measurement at the plot boundary and at openable windows. If the standard is exceeded, the owner is required to take measures.
What noise standard applies to a heat pump in Flanders?+
Daytime (7am to 10pm) maximum 45 dB(A) at the plot boundary, night-time (10pm to 7am) maximum 40 dB(A), always measured at 1.5 metres height. For an audible hum, a tonal penalty of +5 dB is added.
Does an enclosure around a heat pump really help?+
Yes, but the Code of good practice regards a full enclosure as a last resort. An enclosure must be correctly dimensioned with sufficient ventilation, otherwise the unit can freeze up or malfunction. We usually recommend an acoustic screen between the unit and the plot boundary first, combined with absorbing panels. This is more effective and requires less maintenance.
How much decibel reduction can I achieve with an acoustic screen?+
A correctly placed screen or enclosure typically reduces heat pump noise by 10 to 20 dB(A). A reduction of 10 dB(A) is perceived by the ear as a halving of the noise.
What does an acoustic solution for a heat pump cost?+
An acoustic screen between the unit and the plot boundary starts at approximately 200 EUR per m² including installation (excluding VAT). Usually 4 to 8 m² is sufficient. A full enclosure with forced ventilation costs more depending on the size of the unit.
My neighbour has several air conditioning units on the roof. Does that noise add up?+
Yes, noise sources add up logarithmically, not arithmetically. Two units of 40 and 43 dB combine to roughly 45 dB, five units of 45 dB each combine to roughly 52 dB. A roof with multiple units can therefore quickly exceed the Flemish plot boundary standard, even if each unit individually meets the Ecodesign directive. In such cases we usually install an enclosing screen or a shared enclosure per zone.
Does it really help to place the unit further from the plot boundary?+
Yes. Every doubling of the distance between the unit and the listener reduces the sound pressure by roughly 6 dB(A) in open field. In practice the effect is smaller due to reflection against facades and smooth surfaces. Always combine distance with the correct orientation of the air outlet and an acoustic screen for a measurable result below the standard.
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