Research on air source heat pump noise emissions was published on 30 November 2023, leading to a consultation on amendments to MCS-020, the standard used to assess heat pump noise under permitted development rules1.
The publication followed a public consultation that ran from 31 May to 23 August 20231. An independent analysis of the responses to that consultation was published in March 20241. The findings published on 30 November 2023 relate to the third phase of a review of permitted development rights, which the Scottish Government describes as part of its wider planning reform programme1.
The Phase 3 measures are intended to support the deployment of domestic and non-domestic renewables equipment, the alteration or replacement of windows to improve energy efficiency, and the roll-out of electricity network infrastructure1. Class 9M of the General Permitted Development Order, which covers solar canopies and associated battery storage in qualifying parking areas, was introduced through Phase 2 and came into force on 31 March 20231.
The Scottish Government set out its reasoning for the wider package in the policy note accompanying the amending Order:
"In view of the cost and climate crises, the changes introduced by the Order provide additional flexibility for homeowners to install a range of domestic microgeneration equipment without a planning application being required."
The Order amends the Town and Country Planning (General Permitted Development) (Scotland) Order 1992 and was made under sections 30, 31 and 275 of the Town and Country Planning (Scotland) Act 1997. It is subject to negative procedure1.
| Measure | Change under the Order |
|---|---|
| Ground and water source heat pumps (Classes 6D and 6E) | Permitted development now covers associated pipework and other apparatus, not just the pump1 |
| Free-standing wind turbine (Class 6G) | Distance restriction replaced with one based on turbine size: less than 110% of overall height from another dwelling's curtilage; maximum height 15m; lowest blade part at least 5m above ground1 |
| Solar panels on dwellings (new Class 6HA) | Applies in conservation areas, but not to the principal elevation or a side elevation fronting a road1 |
| Solar panels on outbuildings (new Class 6HB) | Panels may not protrude more than 500mm from the wall or roof1 |
| Non-domestic solar (new Class 6J) | Panels may not protrude more than 1m from the building surface1 |
| Free-standing non-domestic solar (new Class 6N) | Total curtilage area limited to 12 square metres1 |
Why it matters for households
Noise is one of the practical constraints on where an air source heat pump can be sited without a planning application, because permitted development normally depends on meeting the MCS-020 noise assessment. The research published on 30 November 2023 and the consultation that follows it concern the method used to make that assessment, so the outcome could affect which properties can install a pump under permitted development and where on the plot it can go. The MCS 020 noise assessment sets out how the calculation works, and how noisy a heat pump is covers the sound levels involved in practice.
The wider package of permitted development changes in Scotland covers ground and water source heat pumps, solar panels and small wind turbines, all of which affect what a household can install without a planning application. The rules differ by nation, and the permitted development rights page explains the position for home energy equipment. Where a conservation area or other designation applies, separate restrictions can remove permitted development altogether, as set out for Article 4 directions.
What happens next
The consultation on MCS-020 amendments follows the 30 November 2023 publication. An independent analysis of responses to the Phase 3 consultation was published in March 20241. The amending Order was made under negative procedure, meaning it takes effect unless Parliament annuls it within the scrutiny period1.