Air Source Heat Pumps – Still Causing Noise Complaints! (Insight)

The old Microgeneration Certified Scheme (MCS) has been revised as of 20th March 2025. MCS will now split the MCS 020 standard into two: one for air source heat pumps and one for small wind turbines (there are no changes to the requirements for small wind turbines). Here’s our thoughts on what has changed with MCS 020 (a), and how these changes may impact you and your developments going forward.

In a drive to meet climate targets, improve efficiency, and reduce emissions, there has been a marked transition towards the use of ASHPs in recent years. Government figures show that in 2024, 52% more ASHPs were installed than in 2023, largely due to government-funded initiatives.

This is, however, a hot (no pun intended) and seemingly ever-present topic for acoustic consultants and local authorities. It also remains open to debate.

THE GUIDANCE GAP

For new-build developments, the race for greener energy and the widespread use of ASHPs appears to have far outpaced the development of any national guidance on assessing the potential acoustic impacts these units can have on neighbouring residential dwellings. More often than not, this is left for local authorities to determine individually, resulting in inconsistent requirements from borough to borough.

To fill this vacuum for Permitted Development purposes, the Microgeneration Certification Scheme MCS-020 (originally created for small-scale wind turbines) was adopted to give installers and homeowners a simplified, ‘one-size-fits-all’ method for assessing the installation of their new heating system.

As expected, this ‘one-size-fits-all’ approach was met with trepidation by our team and other acoustic consultants, and as noise complaints began to increase, local authorities quickly recognised the shortcomings of a generic assessment method. What may be acceptable in an urban setting could be entirely unsuitable in a rural environment.

WHAT’S CHANGED?

Following industry-wide consultation in November 2024 (including but not limited to the CIEH, IOA, ANC, and others), MCS-020 (a) was released on 20th March 2025. While it retains the ‘one-size-fits-all’ concept, it is certainly a step in the right direction.

Key changes include:

• Sound levels now assessed to 37 dB LAeq, 5mins (previously 42 dB).
• Emphasis on using sound power levels, not sound pressure.
• Improved assessment for multiple ASHP installations.
• Clearer definitions of acoustic barriers.
• Updated barrier reduction values.

SO, WHAT DOES IT ALL MEAN?

A 5 dB reduction is significant, and a welcome acknowledgement of the shortcomings in the previous 42 dB threshold.

A key question to ask yourself is, does compliance with this new level ensure there will be no adverse impacts on nearby residents?

In a nutshell, no. Even at 37 dB, installations can (and likely will) lead to noticeable increases in residual sound levels, especially in quieter, rural settings.

You also have to ask if meeting this new assessment would protect your installation from being classified as a Statutory Nuisance in the event of a complaint?

No, it would not. The Control of Pollution Act 1974 and Environmental Protection Act 1990 remain in place to protect all of us—and our amenity—from unwanted sources of pollution, including noise. Statutory Nuisance complaints apply to both residential and commercial properties.

NOT SURE WHERE YOU STAND?

Admittedly, we’re still in a state of limbo regarding the correct assessment methodology for ASHP installations in new developments. However, in our considerable experience, we strongly recommend discussing your plans with the Local Planning Authority (LPA) or Environmental Health Officer (EHO) early, in order to agree on a mutually acceptable approach.

While this updated document is undeniably a step forward for Permitted Developments, we at Create are fully aware that this is not the ‘final boss’ when it comes to ASHP assessment criteria. Some sites will still fall through the cracks, some neighbours will still fall out, and yes—some installers will still get it wrong!

If you’re unsure how these changes impact your project—or concerned you may be at risk—contact our Acoustics team today. Or carry on as you are… and give us a call when it goes wrong! 😊

ABOUT ‘INSIGHT’

‘Insight’ is our way of discussing ongoing challenges and issues facing our industry. These posts will be separate to our usual news and project posts and identified via the ‘Insight’ tag. Our thought pieces will range from discussions on regulations and legislations, laws and governance to national strategy and local policy.