What if my ASHP fails a noise assessment?

Practical options include repositioning, vibration isolation, screening or operational adjustments. Acoustic covers can be costly and are rarely the first choice.

MCS 020 vs BS 4142—what’s the difference?

MCS 020 provides a simplified check (assumes 40 dB(A) background). BS 4142 is the widely accepted planning method that compares ASHP noise to measured background and considers tonality and character.

Essential ASHP Noise Assessment for Air Source Heat Pumps

Q: How noisy are air source heat pumps?

Typical ASHPs produce around 40–60 dB(A) at 1 m. Perceived impact at the neighbour depends on background levels, placement, screening and operation.

Q: Do I need planning permission for an ASHP?

Many domestic ASHPs are permitted developments, but councils may require a BS 4142 noise report where amenity could be affected. Always check your LPA guidance.

Engineer-led assessments to meet BS 4142 and Local Planning Authority requirements. Ensure quiet operation, avoid complaints, and get fast, compliant reports.

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Author & Reviewer: Paul Schmitz MBA CEng MIMechE MIoA, Director & Chartered Mechanical Engineer.

Why an ASHP Noise Assessment Matters

Air Source Heat Pumps (ASHPs) are efficient and eco-friendly, but the outdoor fan (turbulent airflow) and compressor (refrigerant compression) can produce noticeable noise. Without proper assessment, installations may disturb neighbours, breach planning requirements, or lead to costly remedial works.

Local Planning Authorities (LPAs) often request evidence that the installation will not harm residential amenity—typically via a BS 4142 noise impact assessment.

How Noise is Measured: BS 4142 vs MCS 020

MCS 020 (Microgeneration Certification Scheme)

Simplified method assuming a fixed 40 dB(A) background level.
Useful as an initial screening tool for some domestic cases.
Guidance is evolving; always check the latest MCS notes.

BS 4142:2014+A1:2019

Widely accepted by LPAs for plant/industrial noise, including heat pumps.
Compares the ASHP’s specific sound level with measured background (LA90) at the nearest sensitive location.
Applies penalties for character (tonality, intermittency, impulsivity), giving a robust indicator of impact.

Before You Install an ASHP

Check your LPA requirements: policies vary across councils.
Commission an assessment early: confirm compliance before purchase.
Select the right unit: noise emissions vary significantly by model.
Positioning matters: distance, screening and orientation can reduce impact.

If Your ASHP Is Already Installed

LPAs sometimes request a retrospective noise assessment following complaints or site checks. Don’t panic—most issues can be resolved pragmatically:

Reposition or re-orient the outdoor unit.
Add vibration isolation or damping to reduce structure-borne components.
Introduce screening or adjust operating modes/constraints.

Avoid jumping straight to acoustic covers (often £1,500+)—we typically find more cost-effective solutions first.

Our Experience & Insights

Retrospective assessments are common: councils often investigate after complaints.
Policies vary widely: the same system may be acceptable in one area and questioned in another.
Vibration matters: poorly isolated fans and compressors can transmit into structures.
Proactive planning wins: getting a BS 4142 assessment before installation saves time, money and stress.

FAQs

How noisy are air source heat pumps?

Typical ASHPs produce around 40–60 dB(A) at 1 metre (similar to conversation). Whether it’s noticeable at the neighbour depends on background sound, distance, screening and the character of the noise.

Do I need planning permission for an ASHP?

Many domestic units are permitted developments, but LPAs may require a noise report where amenity could be affected. Always check your council’s guidance.

What happens if my ASHP fails the noise assessment?

We’ll propose proportionate mitigation: repositioning, vibration isolation, screening or operational changes. Acoustic enclosures are a last resort.

MCS 020 or BS 4142—what should I use?

MCS 020 is a quick screening method; BS 4142 is the planning-grade approach used by most LPAs, comparing your unit to the measured background and considering noise character.

Led by a Chartered Engineer

Paul Schmitz MBA CEng MIMechE MIoA is a Chartered Mechanical Engineer with decades of experience in vibration, dynamics and acoustics across residential, industrial and infrastructure projects.

Request an ASHP Noise Assessment

Share your proposed unit, location and site plan. We’ll recommend a practical approach and provide a fast, compliant BS 4142 report where required.

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