Five ways to eliminate noise in MVHR systems

One of the biggest complaints homeowners have about ventilation and heat recovery units is noise. In what’s known as ‘dripping tap syndrome’, if someone moves into a property and hears something, they will always hear it. This can be caused by number of sources including ventilation systems such as MVHR.

Noise from MVHR units doesn’t need to be a nuisance – you can easily design out any excess sound. Overall issues with noisy units are caused by shortcuts at the design stage (which is always a false economy), poor installation or blocked filters. Here are our top 5 noise-busting tips when it comes to MVHR

Design out the noise – proactively look at where noise might occur

By addressing key considerations during the initial design process, noise can be eliminated from MVHR systems from the outset, avoiding costly correctional measures later on. If dealing with mass flow isn’t taken into account, the unit’s motor speed may have to be increased along with grille terminations throttled down, which can result in excessive noise. Ensuring ductwork is the right size, limiting the amount of bends in the ducting and utilising coanda effect grilles all helps to reduce the system pressure along with noise levels. In addition, designing in attenuators where appropriate helps to ensure noise is reduced at the source and in individual rooms.

Zehnder ComfoAir 350, MVHR systems, mechanical ventilation and heat recovery
Zehnder ComfoAir 350

Select the right unit and location for the property

It sounds simple, but making sure you choose the right unit for the property is hugely instrumental in eliminating noise. If a unit is too big, its bigger motors will mean more noise, and if the unit is too small, it will have to work harder and faster to be effective, again resulting in breakout noise. Where MVHR units and components are placed within a home can also make all the difference to the level of noise they produce. Units should be located away from noise sensitive areas such as bedrooms, and grilles should be located away from beds where even low noise levels can disturb sleep.

Installation, installation, installation

Good design can all-too-easily be undone on site. At the installation stage it is essential that ductwork is supported and sealed properly, that none of it is crushed, and that excessive lengths of flexible ductwork are not used. Otherwise there may be leakage which requires the unit to be turned up, causing noise, or which builds-up pressure in the system, also increasing noise.

Correct commissioning

Commissioning the unit correctly by following procedures and conducting the right checks, will also help to eliminate nuisance noise.  At the commissioning stage it is vital to balance the supply and extract air, and to set trickle and boost speeds, to help minimise operating noise. It is also essential to check that the correct valves are fitted in each room, and to fine-tune each room grille to meet airflow rates rather than having to turn the unit up.

Remember maintenance!

If an MVHR unit’s filters are allowed to become blocked, it will have to run at higher speeds, raising the levels of noise. To prevent this, and to keep on delivering the healthiest indoor air quality, filters must be cleaned or replaced every six months, or in accordance with the manufacturer’s recommendations. The handover document for the homeowner should explain exactly what’s needed and how often the filters need to be replaced.

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