Appeal 6001072

The appeal is dismissed.

The application form describes the proposed development as “planning application to support install of air source heat pump.” I have rephrased this description in my decision so that it relates to only the development proposed.

The main issue is the effect of the proposed Air Source Heat Pump (ASHP) on the living conditions of future occupiers of the adjacent property, No [address] with regards to noise and disturbance.

The appeal property is a 2 storey mid-terrace dwelling in a predominantly residential area. The proposed ASHP would be located to the rear of the host dwelling. One of the adjoining dwellings, No 93, includes a conservatory adjoining the boundary. A first-floor window serving a bedroom sits above the conservatory. I observed that the conservatory benefits from insulation applied to the inside of its glazing. The bedroom window is double glazed but does include an openable casement and it is this habitable room that is the nearest sensitive receptor to the proposal with no barriers existing or proposed between them.

The effect of the proposal on the sound levels experienced at this receptor has been assessed by the appellant using different methodologies and the results are included in the evidence before me, to which I have had regard. Initially, the [name] (MCS) 020 methodology was used, with a result of 42.32dB at No 93’s bedroom window, which is only marginally above the limit of MCS 020. The evidence also includes a calculation using MCS 020(a) which was introduced following changes to permitted development rights in 2025. The sound level calculated using this methodology is 38.4dB. This is in excess of the 35dB cited by the Council in their decision notice as the recognised maximum acceptable noise level at a sensitive residential receptor. It is also more than the 37dB criterion used as the noise limit in the MCS Planning Standards included in the revised permitted development rights.

The appellant’s evidence also includes a DEFRA road noise map extract, showing that existing baseline background noise levels at sensitive receptors, including No 93’s bedroom window, are at least 40dB. I observed on site the proximity of No 93’s window to the proposed ASHP’s location, and the lack of existing or proposed intervening barrier that would reduce the sound level at this receptor. I also noted that, whilst it was a snapshot in time, the background noise levels at the time of my site visit were relatively quiet during daytime. I have nothing in the evidence before me to indicate that such levels would be any higher after nightfall when the bedroom at No 93 would likely be occupied and, on summer and other warmer nights, the window open. At such times it is highly likely that traffic levels and the resultant noise would decrease. In this regard, the Council’s baseline background noise level position of 30dB-35dB is appropriate.

In the context of the above, informed by the MCS 020 and MCS 020(a) calculations and my experience and observations on site, I find that the proposal would result in harm to the living conditions of No [address] by reason of increases in noise and disturbance. The harm would result in conflict with policy CP57 of the [name] 2015 (WCS). This requires developments to provide a high standard of amenity for existing and future users.

The appellant’s evidence questions whether the MCS 020 and MCS 020(a) methodologies are appropriate. They state that they consistently predict higher sound impact levels when compared to the ISO 9613-2 methodology required for a BS4142 assessment. I acknowledge that an ISO 9613-2 calculation has been included in the appellant’s evidence and shows a sound level below 35dB at different sensitive receptors including the bedroom window at No [address]. However, the Planning for Sound from ASHPs: Options, Risks and Opportunities paper, included in the appellant’s evidence, notes that the ISO 9613 methodology had not been developed to determine sound transmission over the short distances and around multiple building surfaces that are typical of ASHP installations. It also recommended that systematic investigation of sound complaints is necessary to gather concrete evidence on the effectiveness of MCS 020 in real-world scenarios. This paper and the other evidence before me provide no justification that MCS 020 and MCS 020(a) calculations cannot be used to inform my decision.

The appellant also suggests that the recommended 6dB penalty adjustment for character correction, as required by the Council for the calculations, is excessive and that a 2dB penalty should, instead, be applicable for tonality of the ASHP. The Council’s evidence advises that a 6dB penalty is appropriate and proportionate because impulsivity and intermittency must be considered in addition to tonality. The Council’s position is based upon comments from their Environmental Health Officer (EHO) and I have no evidence before me to dispute their specialist expertise.

The Council’s Public Protection consultee has advised that the installation of a barrier which fully blocks line of sight between the neighbouring residential windows and the ASHP would lower the noise levels in respect of the neighbour’s windows. On that basis the Public Protection objection would be removed. However, the Council’s Delegated Report indicates that the appellant has declined to do this due to conflict with the rear amenity space and a potential effect of making the ASHP work harder and therefore emit greater noise. As such it would not be reasonable for me to allow the appeal subject to a condition requiring the provision of such a barrier.

Finally, I acknowledge the benefits of the proposal in terms of the provision of a low-carbon heating solution, which would accord with the aims of policy CP42 of the WCS, the National Planning Policy Framework, and the wider aims of the [name] 2022-2027. However, given the scale of the development, for a single ASHP at a domestic property, any benefits in that regard would be limited and do not outweigh the harm to living conditions that I have identified.

For the above reasons, and having had regard to all other matters raised, I conclude that the appeal should be dismissed.