WarmtepompGeluid
Evening+Night
53
Day
58
dB(A) max LwA

Property

Residential zoning

Outdoor unit

Zb = 1.15 m · Q = 2 · On: Aanbouw

Margin

3 dB

Sound power

Buildings

Garden walls

Left
Right

Receiver positions

No receiver positions. Click '+ Receiver position' on the map to add one.

Buitenunit staat op hoogte - controleer ook ramen/deuren van buurwoningen! Voeg ontvangposities toe op de hoogte van nabijgelegen ramen.

Result

Evening+Night
53
dB(A) max LwA
Day
58
dB(A) max LwA
Qbron = 2 · Margin = 3 dB
Max Lp at boundary: 40 dB(A)
(at LwA = 56)
Side cross-section
Side cross-section — Shows the height of buildings and the sight line from the outdoor unit to the loudest point on the property boundary. There is a clear line of sight between the outdoor unit and the measurement point.

Calculate heat pump noise: unit on an extension or flat roof

The flat roof of an extension is a popular spot for the outdoor unit: out of sight, no garden space lost, short pipe runs. Acoustically, however, it is one of the most difficult setups. The unit sits 3 to 4 metres up and looks straight over fences and garden walls onto the neighbours’ facades and windows.

In this preset the unit starts on a 3-metre extension. Drag it across the roof and see how its position relative to the roof edge and the neighbouring plots drives the result.

How to use the tool for this situation

  1. 1
    Check the extension

    Adjust the dimensions and height of the extension under “Buildings”. The tool automatically detects that the unit stands on its roof.

  2. 2
    Move the unit away from the edge

    The further the unit sits from the roof edge, the more that edge screens the low assessment points at the boundary.

  3. 3
    Add receiver positions at the neighbours’ windows

    Because the source is higher than 2.5 metres, the tool warns you to check upper windows too. Use “+ Receiver position” and set z to the centre height of the window (e.g. 4.5 m for a bedroom window).

  4. 4
    Compare day and night

    The result shows the maximum LwA for both periods. A unit with silent mode may run at the 40 dB level at night and 45 dB during the day.

Why an elevated installation is often unfavourable

At ground level the sound towards the neighbours is often broken by fences, walls and outbuildings. On a 3.75-metre extension that screening largely disappears: there is a clear line of sight from the unit to the boundary and to the first floor of surrounding homes. On top of that, your own rear facade sits right behind the unit and reflects sound — the tool includes that reflection automatically.

The boundary assessment is made at 1.5 metres height. With a high source that point does not tell the whole story: the level at a bedroom window at 4–5 metres can be higher than at the boundary itself. That is why the official method — and this tool, via a warning — requires extra receiver positions at window height whenever the source is above 2.5 metres.

Practical improvements on an extension

If the numbers don’t work out, the most effective measures are: move the unit further from the roof edge (the edge starts acting as a screen), add a small parapet or acoustic screen around the unit (closed, at least 10 kg/m²), choose a unit with lower sound power, or fit an acoustic enclosure (enter its attenuation as D omkasting under “Equipment specs”).

Mind vibrations too: a unit on a lightweight roof can transmit structure-borne noise into your own house and — with a shared extension wall — into the neighbours’. Vibration dampers are almost always needed on roof installations. This is outside the airborne calculation of this tool but is a common source of complaints in practice.

How does the calculation work?

The calculator is based on WPAC-geluid V2020, the official Dutch calculation tool for noise from outdoor heat pump and air-conditioning units, developed for the Ministry of the Interior. It computes the sound transmission loss (D) from the outdoor unit to each assessment point: the larger the transmission loss, the more sound power the unit is allowed to produce.

Distance is the dominant factor: every doubling of distance reduces the level by 6 dB. The directivity factor Q also matters — a unit within 2.5 metres of one wall (Q=1) is 3 dB louder than a free-standing unit (Q=2), and a corner between two walls (Q=0.5) adds another 3 dB. Reflections from building walls raise the level, while buildings between the unit and the assessment point screen the sound.

The transmission loss yields the maximum allowable sound power (LwA) of the unit: max LwA = limit + D − margin. The safety margin (default 3 dB, minimum 2 dB) covers design and measurement uncertainty. Compare the calculated maximum with the sound power on the unit’s energy label or product documentation.

The noise limits in brief

Since 1 January 2024 the noise requirements for heat pumps and air conditioners are set by the Besluit bouwwerken leefomgeving (Bbl), the successor to the Dutch Building Decree 2012. Article 4.107(2) Bbl states that an outdoor heat or cold generation installation may cause at most 40 dB at the boundary with a neighbouring residential plot. For situations on the same plot — such as apartment buildings — the same limit applies at openable windows and doors of another dwelling (article 4.108(3) Bbl).

The 40 dB limit applies in the evening and at night (19:00–07:00). If the unit has a low-noise setting (silent mode) active during that period, a limit of 45 dB applies during the day (07:00–19:00). Without silent mode the unit must meet 40 dB during the day as well. Read more on the heat pump noise limits page.

Frequently asked questions about this situation

Is a heat pump allowed on an extension at all?

The same noise limit applies as anywhere else: at most 40 dB at the boundary (evening/night). The installation itself may additionally require a permit depending on visibility from public space and municipal rules. Check with your municipality.

Why do I need to check the neighbours’ windows?

The legal assessment point is at the boundary at 1.5 m height, but with a high source the level at upper windows can be higher than at the boundary. The official WPAC method therefore requires receiver positions at windows and doors whenever the source is above 2.5 metres.

Does the roof edge act as a noise screen?

Yes — if the unit stands well back from the edge, the edge breaks the sight line to low assessment points and screens the sound. The tool calculates this automatically. It does not help for upper windows, which keep a clear view of the unit.

Does the reflection from my own rear facade count?

Yes. A wall directly behind or beside the unit reflects sound towards the neighbours and raises the level by several dB. The tool detects walls within 2.5 metres and adjusts both the directivity factor and reflections automatically.

Calculate other situations

In the garden On outbuilding On the roof Apartment

Further reading

This calculator provides an indicative result based on WPAC-geluid V2020 and does not replace a formal acoustic study. When in doubt, consult an acoustic consultant or your municipality.