Case study

Air Source Heat Pumps - A Complex Challenge

Silent Solutions: Navigating Noise Compliance for Heat Pumps

Our client was seeking planning permission to install five air source heat pumps as part of a wider renovation of their three-storey detached family home in London, situated near Heathrow Airport. As part of the planning process, the local authority requested a detailed noise impact assessment to demonstrate compliance with stringent acoustic criteria.

The specific requirement was that noise from new mechanical plant, including ventilation, must not adversely affect neighbouring properties and must be at least 10 dB below the background noise level, in accordance with British Standard 4142:2014+A1:2019 “Methods for rating and assessing industrial and commercial sound”.

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Transport Planning
Infrastructure Design
Environmental Assessment

Details

Sound Traps and Tight Gaps: The Project Challenges

The proposed installation site presented multiple acoustic challenges:

Narrow Space: The air source heat pumps were to be installed at ground level in a narrow 1.5-metre-wide gap between the client’s home and the neighbouring property.
Noise Canyon Effect: Although there were no windows on the side façades, the proximity of the buildings created a ‘noise canyon’, a phenomenon where sound waves bounce and reflect between tall, close structures, potentially amplifying the overall noise levels.
Complex Modelling: Due to the complex acoustic environment, a simple spreadsheet-based assessment was insufficient. Advanced 3D noise modelling software was required to accurately predict sound propagation and assess compliance.

Smart Enclosure Solutions: A Tailored Approach to Urban Noise Challenges

We developed a detailed noise model of the site, incorporating the air source heat pump specifications, environmental conditions and building geometry. The initial results revealed that the predicted noise levels exceeded the local authority's strict criterion of 10 dB below background.

To address this, we worked closely with the client and their architect to place the air source heat pumps into a suitable acoustic enclosure, which was designed to:

mitigate noise emissions to acceptable levels;
maintain sufficient airflow for the air source heat pumps to operate; and
fit within the spatial constraints of the site, whilst ensuring that suitable access could be maintained.

Getting It Right from the Start: Critical Elements in a Complex Noise Assessment

Mayer Brown added value for our client by:

Establishing the local authority’s requirements early in the project, particularly given the stringent noise criteria.
Identifying at the outset, that a simple spreadsheet-based assessment would not suffice due to the narrow space between the properties and the resulting “noise canyon effect”.
Selecting the most appropriate assessment method, 3D noise modelling, to allow us to accurately evaluate the impact of the proposed air source heat pumps.
Working closely with the client and their architect throughout the project, which was an essential part of the process.

Sound Traps and Tight Gaps: The Project Challenges

Smart Enclosure Solutions: A Tailored Approach to Urban Noise Challenges

Getting It Right from the Start: Critical Elements in a Complex Noise Assessment

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