MHVR and Noise

[Tony K]

Afternoon.

I have received a range of quotes for an MHVR kit for my SB, which is a 100m2, flat roofed bungalow. The roof is made using posi joists, through which the MHVR system can be fitted. 

The quotes (for design and supply only) range from under 2k up to over 6k. Both the highest and lowest quotes stress the importance of avoiding a noisy system, and claim to offer it. 

 

Has anyone had any issues with noise from the MHVR system?

Any advice on avoiding noise, and/or what to look for when choosing a system?

 

Thanks

[Iceverge]

Issues.

 

1 Vibration from the units and

2.Noise through the ducts. 

 

Solutions

 

1. Floor mount the unit, mount the unit on an external wall or hang the unit from wires or use rubber feet. 

 

2. Avoid very high flow rates through too small ducts. Use acoustic silencers. Metal ones aren't too dear. Or make your own. 

 

 

 

 

[Conor]

Oversize everything. Use attenuators at the unit and use vibration eliminating couplers (leather or rubber) at the unit. Mineral wool insualtion around the ducts.

[JohnMo]

Long pipe runs mean, bigger pressure drops, which mean for a given flow rate the MVHR unit needs to work harder, so makes more noise.  Consider 90mm if going semi flexible.

 

You haven't mentioned what the piping is.  There are several options.

 

Semi flexible, comes with a plenum, this reduced cross talk between rooms, is easy to install.  Other systems will require multiple attenuators/ silencers between rooms.  If any quotes specify flexible duct, don't use them.  High pressure drops, so not good.

[Adam2]

Will depend on plans for duct serial or radial.

If using smaller diameter semi-flex duct on a radial plan (seems pretty common) - put your distribution boxes somewhere central to minimise the lengths of smaller duct running to the outlets/inlets. Use rubber or silicone connections on the runs to the distribution boxes (help with angles + reduces noise to some degree) + the dedicated silencer sections.