Heat Pump Noise MCS-020 Explained — London Planning

MCS-020 is the Microgeneration Certification Scheme procedure for calculating noise from a heat pump installation. It produces a single number — predicted sound level at the nearest neighbour's window or door — measured in dB.

If MCS-020 calc shows the predicted level is below 42 dB at the nearest assessment point, the install qualifies for permitted development under the Town and Country Planning (General Permitted Development) Order.

Without an MCS-020 pass, the install requires planning permission. Plus 8-12 week delay, £200-450 in fees, and uncertain outcome.

Inputs: heat pump model (manufacturer's published sound power), distance from heat pump to nearest assessment point, number and material of intervening walls, ground absorption.

Standard MCS-020 calc tool walks through each input. The result is a predicted dB(A) value at the assessment point.

Most modern ASHPs (Vaillant Arotherm, Daikin Altherma, Mitsubishi Ecodan) publish sound power figures that allow MCS-020 to pass at 3-5m distance with one wall in between.

Older or larger units may struggle. A 16 kW ASHP at 1m from a neighbour's window is unlikely to pass without acoustic shrouds.

Mid-terrace house, ASHP on rear garden wall, neighbour 8m away. MCS-020 passes comfortably with most modern units. Permitted development.

Semi-detached, ASHP on side wall facing neighbour 4m away. Marginal — choose a quiet model (Vaillant Arotherm Plus, Daikin Altherma 3 RF) and the calc usually passes.

Terraced with shared rear elevation, ASHP 2m from neighbour window. Often fails — needs acoustic shroud (£400-800 extra) or planning permission.

Flat with balcony, ASHP on balcony or roof. Usually fails because no horizontal distance to neighbours. Plan for full planning application.

Reposition. Move the ASHP further from boundaries or onto a façade with no neighbour assessment point. Often increases pipe runs and cost.

Acoustic shroud. Manufacturers (Vaillant, Grant) sell purpose-built acoustic enclosures that drop noise 6-12 dB(A). £400-800 extra. Often turns a failing calc into a passing one.

Quieter model. Some models (Vaillant Arotherm Plus, Daikin Altherma 3 R/RF) are 3-5 dB quieter than competitors. May add £500-1,000 but avoids planning permission.

Planning permission. Last resort but works in 60-70% of cases in our London experience. Council prefers heat pumps over fossil fuel; refusal must be substantively justified.

Pre-install conversation — share the MCS-020 result, show the predicted dB level, demonstrate that 42 dB is below the standard noise threshold for residential areas.

Compare with existing noise sources. A gas boiler flue, AC condenser, or fridge condenser running outdoors are similar or louder. Most people accept this comparison.

Offer a noise survey post-install. A 30-minute measurement at neighbour's window with a calibrated meter (£150-250) provides actual evidence and usually resolves disputes.

If neighbour formally objects to council — share MCS-020 paperwork, environmental health rarely rules against a passing calc.

MCS-020 noise calc PDF with all inputs and the calculated dB result. Keep in the property file.

Photo of ASHP location showing distance to nearest assessment point.

Manufacturer's published sound power data sheet.

Permitted development checklist (most councils have a downloadable form).

If you needed planning permission — the granted decision notice and any conditions attached.