MVHR wall mount - vibration

[hauntedicecreamvan]

I am fitting MVHR to a bungalow. Originally it was going into a kitchen wall cabinet (it's a Zehnder Comfoair 180) but duct runs are much nicer if I install it in the former airing cupboard. The airing cupboard is 600x600 and blockwork on all three sides. These walls back onto the bedrooms.

 

Due to the location of a ceiling joist, the MVHR unit needs to sit forward from the back wall roughly 150mm. This allows the ducts to pass straight up without additional 45 degree turns.

 

Given the proximity to bedrooms, and the 150mm of dead space behind the unit, I was wondering if it is worthwhile building some isolation in between the blockwork and unit?

 

I was going to build a timber frame fixed directly to the back and side walls, filled with Rockwool RWA45, and faced with 18mm plywood. But that doesn't do anything to physically isolate the unit from the wall, only added mass, and does this risk making the frame become a mini stud wall that resonates more than the blockwork would?

 

Is it worthwhile going through the effort of building a "floating" timber frame to mount the MVHR unit on, with spring/rubber mounts to keep it in place?

 

Any advice or tips welcome.

Edited February 5 by hauntedicecreamvan

[JohnMo]

I have an MVHR in a hall cupboard, but with a bedroom either side. My walls are wooden stud walls.  The mounting face for the MVHR, has a double layer of 18mm ply. The stud walls are filled with Rockwool Flexi and 12.5mm plasterboard elsewhere. No vibration and zero noise. I did not use anti vibration mounts.

[hauntedicecreamvan]

Thank you, sounds like I might be overthinking this. I should probably just build a basic frame offset from the wall for now, and pack behind with Rockwool, faced with plywood like yours.

[JohnMo]

Why not make something self supporting and not touch the walls at all, something like this, but make it nice and solid 

 

[saveasteading]

Acoustic rail / resilient bar is useful in stopping vibrations carrying through

 

I once had a roll of a bitumen sort of sheet with lead trapped within. It was made for medical aprons to stop x-rays.

Very heavy but also flexible, and I used it on a party wall , hung loose behind the plasterboard, to great effect.

It isn't available and would be crazily expensive, but some other heavyish loose material could be used. thick polyethene etc.

 

 

[Nickfromwales]

Brink and Zehnder stuff is very well made and PH certifiable, so are very quiet and quality bits of kit.

 

Why are you worried about adding the 45° bends? Just mount on the masonry wall and save all this trouble!!

[hauntedicecreamvan]

34 minutes ago, Nickfromwales said:

Brink and Zehnder stuff is very well made and PH certifiable, so are very quiet and quality bits of kit.

 

Probably just paranoia about getting it right first time. My current Nuaire Drimaster 365 PIV is mounted on ceiling joists and the basic sponge isolators supplied with the unit did nothing to stop the hum. I ended up with a slab of 38mm worktop and aftermarket anti-vibration mounts to get it quiet enough in the room below.

 

34 minutes ago, Nickfromwales said:

Why are you worried about adding the 45° bends? Just mount on the masonry wall and save all this trouble!!

 

Partly I was concerned about the added height, but also I wanted to avoid as many additional bends as possible. However, I can see from the Zehnder ComfoPipe curves that the pressure loss is minimal at my normal background rate.

 

The ducting and adapters arrived this morning, and it looks like it might just fit, the front pair of ducts clear the joist with a 45-45 "S" sweep. The rear ducts would require a short length of pipe between the two 45 degrees, and I need to check if they then hit the front ducts because they overlap when viewed from above.

 

I probably need to model this in 3D space in CAD to know for sure. The will be a bit of wiggle room to play with because the cupboard is actually around 640mm wide wall-to-wall.

Edited February 6 by hauntedicecreamvan

[Nickfromwales]

43 minutes ago, hauntedicecreamvan said:

 

Probably just paranoia about getting it right first time. My current Nuaire Drimaster 365 PIV is mounted on ceiling joists and the basic sponge isolators supplied with the unit did nothing to stop the hum. I ended up with a slab of 38mm worktop and aftermarket anti-vibration mounts to get it quiet enough in the room below.

 

 

Partly I was concerned about the added height, but also I wanted to avoid as many additional bends as possible. However, I can see from the Zehnder ComfoPipe curves that the pressure loss is minimal at my normal background rate.

 

The ducting and adapters arrived this morning, and it looks like it might just fit, the front pair of ducts clear the joist with a 45-45 "S" sweep. The rear ducts would require a short length of pipe between the two 45 degrees, and I need to check if they then hit the front ducts because they overlap when viewed from above.

 

I probably need to model this in 3D space in CAD to know for sure. The will be a bit of wiggle room to play with because the cupboard is actually around 640mm wide wall-to-wall.

The unit you’re buying is a totally different beast to the “bread & butter” Nuaire unit. 

[JohnMo]

42 minutes ago, hauntedicecreamvan said:

probably need to model this in 3D space in CAD to know for sure.

Really? Just get on get it done.

[Nickfromwales]

On 06/02/2026 at 12:38, JohnMo said:

Really? Just get on get it done.

My thoughts too,  , was just trying to be gentle but yea, agreed, go buy some bends and GTF on with it. 
 

@hauntedicecreamvan, have you allowed for some attenuators to keep operational noise down at the terminals? 

[hauntedicecreamvan]

I drilled an exploratory hole to pinpoint exactly where the joist is, and it's 170mm from the face of the wall. There is enough space to just do a simple S bend using two 45 bends, keeping all ducts parallel and the same length up through the ceiling.

 

I have decided to use multiple sheets of 18mm ply, with green glue and between each layer. The bottom layer will be use Fischer DuoXpand fixings into the blocks and some OB1. Just need to work out if I need 3no or 4no 18mm sheets to pad things out enough.

 

I note that Zehnder specify a mass of 200kg/m2 for the wall, which suggests that 4 sheets is needed when combined with the awful 1970s blocks.

 

Does this sound sensible?

[hauntedicecreamvan]

On 06/02/2026 at 12:40, Nickfromwales said:

have you allowed for some attenuators to keep

operational noise down at the terminals? 

Yes, 900mm Lindab inline attenuator first, followed by Comfowell attenuator manifold.

 

Ducting is 90mm semi-rigid, with Zehnder Luna valves.

Edited February 8 by hauntedicecreamvan

[Nickfromwales]

1 minute ago, hauntedicecreamvan said:

Yes, 900mm Lindab inline attenuator first, followed by Comfowell attenuator manifold.

 Box attenuator or fluffy sock type?

[hauntedicecreamvan]

12 minutes ago, Nickfromwales said:

 Box attenuator or fluffy sock type?

Rigid spiral type - Lindab SLXU.

Edited February 8 by hauntedicecreamvan

[Nickfromwales]

27 minutes ago, hauntedicecreamvan said:

Rigid spiral type - Lindab SLXU.

Happy days.