MVHR Noise Levels: What’s Acceptable and How to Prevent Complaints

Why Noise Complaints Are the Hidden Risk in MVHR Systems

MVHR (Mechanical Ventilation with Heat Recovery) systems are designed to improve indoor air quality, reduce heat loss, and support low-carbon living. But for many homeowners across Reading, Newbury, and West London, poor acoustic design can turn a smart energy decision into a persistent annoyance.

The single biggest source of post-installation complaints about MVHR systems is noise.

Whether it's humming from the unit, air turbulence through ducts, or draughty vents near beds, noise issues arise when systems are installed without proper planning. Yet, noise control is not just a comfort feature—it’s a legal and technical requirement under UK Building Regulations.

This blog explores what’s considered acceptable in terms of MVHR noise, how it should be measured, and what design measures can prevent problems in both residential and commercial environments.

Understanding Acceptable MVHR Noise Levels

The Standards That Define Acceptable Noise

According to Building Regulations Approved Document F, MVHR systems must not cause "disturbance" to occupants. But for precise figures, designers turn to:

• BS EN 13141-7: Acoustic testing standards for residential ventilation
• CIBSE Guide B: Internal noise level recommendations
• BS 8233: Acceptable internal noise levels by room type

Recommended MVHR noise limits:

• Living Rooms: ≤ 30 dB(A)
• Bedrooms (night): ≤ 25 dB(A)
• Kitchens and Bathrooms: ≤ 35–40 dB(A)

Anything over 35 dB(A) in sleeping spaces is likely to be perceived as disruptive by most users. The goal is for systems to run inaudibly at normal ventilation rates.

Where MVHR Noise Comes From

There are three key sources of noise in an MVHR system:

1. Fan Noise from the Unit
   Caused by the internal fan motor, especially when running at high speeds. Lower-quality units often generate more fan hum.
2. Duct Airflow Noise
   Created when air moves through ductwork too fast, especially around tight bends or undersized ducts.
3. Terminal and Valve Noise
   Occurs at ceiling valves when air pressure is too high or the vent is wrongly located (e.g. directly above a bed).

All of these issues can be addressed with proper design, specification, and installation practices.

Case Study: Resolving Noise in a Loft-Installed MVHR System – Guildford

A customer in Guildford contacted ClimateWorks after installing an MVHR system as part of a rear extension and loft conversion. While the system was effective, the master bedroom experienced a constant hum at night.

We identified the following issues:

• The unit had been mounted on timber joists without acoustic isolation
• Supply air duct passed through the bedroom ceiling void at high velocity
• No silencers had been fitted between the unit and the rooms

Our resolution:

• Fitted anti-vibration mounts beneath the unit
• Re-routed ductwork using semi-rigid, acoustically lined ducting
• Installed silencers on both supply and extract ducts
• Rebalanced airflow and re-commissioned the system

Result: Noise in the bedroom dropped from 36 dB(A) to 22 dB(A)—below the BS 8233 guidance limit.

Designing for Low Noise: What the Guidelines Require

An MVHR system should be designed for quiet operation, not just installed. Key acoustic principles include:

• Correct duct sizing: Prevents high velocity air noise
• Flexible anti-vibration connectors: Between duct and unit
• Acoustic insulation: Especially in bedrooms and living areas
• Strategic valve placement: Avoiding direct overhead supply in sleeping areas
• Low-speed settings for background ventilation: With boost modes only on demand
• Silencers: Fitted near the MVHR unit and before air enters habitable rooms

Each of these elements contributes to reducing overall system sound power and eliminating noise at the source.

Bullet Summary: Common MVHR Noise Issues and Fixes

• Unit noise → Mount unit on anti-vibration pads
• Duct hum → Use oversized ducts and gradual bends
• Terminal noise → Relocate vents or fit silencers
• Overboosting → Adjust controller settings to match occupancy
• Commissioning faults → Rebalance airflow to match room sizes

What Happens If Noise Isn't Controlled?

Ignoring MVHR acoustics can lead to:

• Building Control refusing sign-off under Part F
• Occupant dissatisfaction or complaints
• Negative property feedback in rentals or resale
• Early system shutdown or underuse due to irritation
• Warranty risks if acoustic performance wasn't met

At ClimateWorks, we never leave noise control as an afterthought. We treat it as essential to both compliance and comfort.

Our Low-Noise MVHR Installations in the South East

We’ve installed quiet, compliant MVHR systems across:

• West London (Chiswick, Kensington, Acton)
• Surrey (Woking, Camberley, Godalming)
• Hampshire (Basingstoke, Alton, Andover)
• Berkshire (Reading, Wokingham, Bracknell)

Our systems meet or exceed BS 8233 and are commissioned to full Part F standards. We supply MVHR units from trusted brands with proven low-noise credentials and offer a post-installation acoustic performance check on request.

👉 Contact ClimateWorks for a low-noise MVHR quote

References

[1] GOV.UK – Ventilation: Approved Document F
https://www.gov.uk/government/publications/ventilation-approved-document-f

[2] CIBSE Guide B: Heating, Ventilation and Air Conditioning
https://www.cibse.org/knowledge/guide-b-heating-ventilation-air-conditioning

[3] BS 8233 – Guidance on Sound Insulation and Noise Reduction for Buildings
British Standards Institution

[4] NHBC Foundation – MVHR in Modern Homes
https://www.nhbcfoundation.org/publication/mechanical-ventilation-with-heat-recovery-in-new-homes/

Author Bio

Dr. Julian Carter is a highly experienced thermal systems expert with over 15 years in the field, holding a PhD in thermal systems. His career spans academic research, consulting, and teaching, focusing on air conditioning and refrigeration systems. Dr. Carter bridges the gap between theoretical advancements and practical applications, providing expert insights to organisations like ClimateWorks, where his guidance informs decision-making and industry best practices. Notably, he has worked on international projects with organisations such as Daikin Industries, the International Institute of Refrigeration (IIR), and the United Nations Environment Programme (UNEP). Currently a lecturer at Edinburgh University, Dr. Carter combines his expertise with a passion for educating the next generation of engineers and advancing climate control technologies.

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