Appeal 6002727

The appeal is dismissed.

Planning permission was granted on 7 August 2025 for the retrospective installation of four air-conditioning condenser units at ground floor level on the western elevation of a commercial premises. Condition 2 requires the plant to be maintained in accordance with RBA Acoustics Plant Noise Assessment 14564.RP01.PNA.1 Rev.1 dated 25 July 2025. The condition was imposed to protect the living conditions of the residential occupiers of the upper floor flats, whose nearest windows are located approximately 3.5 - 5 metres above the condenser units.

The appellant seeks to vary condition 2 by substituting the approved acoustic report with a later [name] report (Ref. 14564.RP01.PNA.4, dated 11 September 2025), which proposes an alternative mitigation arrangement. The Council refused the application on the basis that the variation would lead to unacceptable noise disturbance to neighbouring residents on the upper floors.

As the appeal concerns development already carried out in breach of the condition, it is appropriately considered under section 73A of the Act.

The Council’s refusal notice refers to London Plan Policy D4 Noise. This is evidently a typographic error, as the correct noise policy is D14. I am satisfied that no party has been prejudiced by this minor error.

The main issue is whether the proposed variation of condition 2 would safeguard the living conditions of neighbouring residents, with particular regard to noise.

Permission was originally granted on the basis of the [name] assessment dated 25 July 2025, which identified background sound levels at first-floor height and established facade noise criteria of 33 dB LAeq by day and 31 dB LAeq by night at 1 metre outside the nearest first-floor residential window above the units. Unmitigated plant levels were predicted to exceed those criteria. Compliance was therefore dependent upon the installation of full acoustic enclosures to each of the four units, providing an overall reduction of 26 dB. The cumulative levels following mitigation were predicted at 31 dB by day and 23 dB by night. Condition 2 secures that outcome by requiring the plant to be maintained in accordance with that report.

The variation seeks to substitute a later RBA report dated 11 September 2025. This records that compressor elements have been relocated indoors and proposes a different mitigation strategy comprising a solid acoustic screen above and to the sides of the units. Using revised source levels and assumed frequency-dependent attenuation from the screen, the report predicts cumulative levels of 31 dB by day and 31 dB by night. The appellant submits that this represents a more cost-effective solution whilst still meeting the Council’s plant noise criteria.

Both the approved and the later assessments measured background sound in free field conditions at first-floor height using a microphone positioned closer to the road than the residential facade. No facade correction or justification is provided to demonstrate that the measurement location reflects the potentially quieter conditions immediately outside the residential windows. In circumstances where the revised assessment relies on predicted noise levels sitting precisely on the night-time criterion, the absence of such explanation reduces confidence that the criteria have been derived from a worst-case position.

Notwithstanding this, the more substantive concern lies with the proposed change in mitigation. The approved scheme relies on full acoustic enclosures of known performance, whereas the revised scheme depends upon a partially specified screen above and to the sides. The later report refers to minimum surface density requirements but no construction drawings, product data, or details of internal lining, sealing to the ground or wall, or the treatment of openings were submitted. As a result, the acoustic performance of the screening has not been demonstrated to an appropriate or enforceable standard.

At my site visit, I observed a structure comprising flat cement-type boards over the top and sides of the units, with open wire mesh across the front and a visible gap between the structure and the wall. Its somewhat crude appearance did not resemble a purpose-designed acoustic installation and nothing before me confirms that it is capable of achieving the attenuation levels assumed in the revised report. As the predicted night-time level sits exactly on the criterion, there is no margin for constructional tolerances, plant variability or operational differences. The Environmental Health consultee raised concerns that the revised arrangements would not provide sufficient attenuation compared with the approved enclosures, and I attach significant weight to that professional advice.

Although the appellant indicates that moving the compressors indoors has reduced noise levels from the units, the submission contains no suitable plans or details that would allow the Council to enforce or ensure the permanence of this arrangement. The approved permission allows four condensers and the revised assessment contemplates the removal or substitution of one unit. Any varied condition must remain effective should the lawful number of units operate, without relying on operational controls outside planning regulation. On the evidence before me, the revised package does not meet that standard or provide assurance that the level of mitigation secured by condition 2 would be maintained.

Paragraph 198 of the National Planning Policy Framework (the Framework) expects planning decisions to mitigate and reduce to a minimum potential adverse impacts resulting from noise from new development and to avoid noise giving rise to significant adverse impacts on health and the quality of life. This is reflected in Policy D14 of the London Plan (2021), Policy CP32 of the [name] (2010) and Policy DMD68 of the Enfield Development Management Document (2014). On the basis of the evidence before me, the alternative mitigation has not been convincingly shown to deliver an acceptable level of noise protection to neighbouring residents. The condition as originally imposed therefore remains necessary, relevant, reasonable and enforceable.

For the reasons given, I conclude that the proposed variation of condition 2 would not secure adequate noise mitigation or protect the living conditions of neighbouring occupiers, particularly at night. It therefore conflicts with the Framework and with the development plan when read as a whole. Accordingly, the appeal should be dismissed.