Noise levels and planning

One of the most common concerns about air source heat pumps is noise. However, modern units are very quiet—often no louder than a low hum or a library. Most installations do not require full planning permission as they fall under “Permitted Development.”

Planning permission rules

In England, air source heat pumps are usually considered Permitted Development, meaning you don’t need to apply for planning permission if you meet several criteria:

  • Size: The outdoor unit must not exceed 0.6 cubic metres in volume.
  • Location: The unit must be at least 1 metre from the property boundary.
  • Quantity: There is only one heat pump on the property (including any air conditioning units).
  • Listed buildings: You usually need planning permission (and listed building consent) if your home is listed or in a conservation area.

Note: Rules differ in Scotland, Wales, and Northern Ireland. Always check with your local planning office if you are unsure.

Managing noise (MCS 020)

To qualify as Permitted Development, the installation must also comply with the MCS 020 noise standard. This ensures that the noise level at the nearest window of a neighbouring property does not exceed 42 decibels (dB).

Factors that affect noise:

  1. Unit quality: Premium brands often use larger, slower-moving fans and better acoustic insulation to reduce noise.
  2. Mounting: Using rubber “anti-vibration” feet or brackets prevents the sound from vibrating through the walls of the house.
  3. Positioning: Placing the unit in an open area rather than a narrow alleyway prevents sound from echoing off hard surfaces.

Ground source heat pumps

Ground source systems typically do not have any planning restrictions related to noise, as the heat pump itself is usually located inside the house (e.g., in a utility room or garage) and has no external fans. However, the excavation work may require permission if you live in a protected area.

Tips for a quiet installation

  • Don’t place the unit directly under a bedroom window.
  • Use a solid base: A heavy concrete plinth absorbs more vibration than wooden decking.
  • Acoustic covers: If noise is a major concern, specialist acoustic hoods can be installed to further dampen the sound.