MVHR Noise

2nd April 2019

Clients often ask how noisy are your MVHR Units? In order to answer this question, we need to explain what the different types of noise issues in ventilation are.

Firstly it is important to look at it as a complete system, rather than a single MVHR unit. Good duct specification and design plays a huge part in how efficient and noisy an MVHR system is.

The Brink MVHR units have constant volume fans, which operate by constantly assessing the system pressure and adjusting the fan to maintain the commissioned airflow. A poorly designed duct system adds to the system pressure and in turn forces the unit to run at a higher speed, thus making it noisier.

It is important to size the duct appropriately; relatively large volumes of air are being moved through the system and using a larger duct may be used to keep in-duct air velocities lower. Trying to push too much air down a small duct means high velocities and increased noise.

Unnecessary bends, sharp bends and corrugated ducting also result in higher levels of resistance in the MVHR system, which increases the noise from the unit and turbulent noise generated by the airflow.

If a branched ducting system is not designed correctly with appropriately placed attenuation, sound can be transferred between rooms – this is known as cross-talk. A radial ducting system with a smooth inner core and manifold for distributing air reduces system pressure and helps prevent cross-talk issues.

It is also important that the unit be maintained. If filters aren’t cleaned regularly, it will result in increased pressure on the fans, which again will lead to increased unit noise.

Finally, it is important to choose an appropriately sized unit for the property; an undersized unit will have to work harder to provide adequate airflow.