MVHR drone

[JohnMo]

I've had good service from duct store 

[Nick Laslett]

1 hour ago, JohnMo said:

I've had good service from duct store 

 @S2D2, I bought all my spiral ducting form the Duct Store, like @JohnMo.

 

https://www.ductstore.co.uk/acatalog/Attenuators.html
 

They have attenuators. 
 

I used the Lindab Safe Click system, which has rubber gaskets. I bought all these components direct from Lindab. Just find the nearest sales office to you. 
 

https://www.lindab.co.uk/Products/ventilation/Sound-attenuation/?sort=popularity&display=16&page=1

 

They have a huge choice of attenuators. 
 

If you want to be confident that you are going to cut most of the MVHR unit sounds before they hit the manifold, you need an attenuator that is 1000mm long. If you look at the spec sheet for the Lindab Attenuator, the difference between 500mm and 1000mm is significant. 
 

A semi-flexible radial system will also help mitigate the noise. Also, you don’t want your individual ducts going to a supply outlet being too short. 

 

Here is a photo from one of @Nickfromwales installs showing 500mm attenuators, foam insulated ducts and a Ubbink manifold. 
 

Edited October 7 by Nick Laslett

[Nickfromwales]

2 hours ago, Nick Laslett said:

 @S2D2, I bought all my spiral ducting form the Duct Store, like @JohnMo.

 

https://www.ductstore.co.uk/acatalog/Attenuators.html
 

They have attenuators. 
 

I used the Lindab Safe Click system, which has rubber gaskets. I bought all these components direct from Lindab. Just find the nearest sales office to you. 
 

https://www.lindab.co.uk/Products/ventilation/Sound-attenuation/?sort=popularity&display=16&page=1

 

They have a huge choice of attenuators. 
 

If you want to be confident that you are going to cut most of the MVHR unit sounds before they hit the manifold, you need an attenuator that is 1000mm long. If you look at the spec sheet for the Lindab Attenuator, the difference between 500mm and 1000mm is significant. 
 

A semi-flexible radial system will also help mitigate the noise. Also, you don’t want your individual ducts going to a supply outlet being too short. 

 

Here is a photo from one of @Nickfromwales installs showing 500mm attenuators, foam insulated ducts and a Ubbink manifold. 
 

I added a 3rd attenuator to that job, as the client wanted “graveyard in Gravenhill” levels of shhhhh! at night.

 

Then foam duct defo helps out, but I’m now being ‘directed’ towards spiral galv rigid ducting against my will…..

 

I’ll do one and see if it passes muster, if not I’ll be reverting back to foam. 

[Jolo]

I also experienced a droning noise, but after buying a rectangular attenuator from Lindab (thanks to your photos and advice here @Nick Laslett and @Nickfromwales!) which didn't stop it, I determined that it wasn't coming from the main unit, but was being generated within the green ribbed Ubbink Air Excellent ducting.

 

So for the bedroom I added a 1m flexible attenuator at the end, just before the vent, and it works great. To avoid adding too much more static pressure I went for one with a 100mm internal diameter (larger than the 75mm internal diameter of the ducting). It works really well, even on boost it's barely audible and at night we don't have it that high anyway, so it's totally silent.

 

I since added another to one of the living room vents, and it's worked great there too.

 

While this does work, is there anything I'm missing? Is there a reason I've never seen this recommended anywhere? 

[Mike]

8 hours ago, Jolo said:

Is there a reason I've never seen this recommended anywhere? 

Because it's cheaper to centralize the attenuators, rather than installing them per-room. And noise generated within the duct would normally be due to excess air velocity, which shouldn't happen - but you seem to have found an exception :)

[JohnMo]

8 hours ago, Jolo said:

at night we don't have it that high anyway

If at night you can turn down the MVHR aren't you actually running too high in general. There should be zero reason to change base rate at different times of the day.

 

Get a simple co2 monitor and move about at different times of the day. And actually look at what is occurring and tune the flow based on actual needs.

 

I am using Ubbink duct, no noise. You have either under installed ducts based on your flow rates or you are flowing to high a rate.

[Jolo]

On 16/10/2025 at 23:23, JohnMo said:

If at night you can turn down the MVHR aren't you actually running too high in general. There should be zero reason to change base rate at different times of the day.

 

Get a simple co2 monitor and move about at different times of the day. And actually look at what is occurring and tune the flow based on actual needs.

 

I am using Ubbink duct, no noise. You have either under installed ducts based on your flow rates or you are flowing to high a rate.

 

Except when cooking/showering/toiletting, we generally keep it on the lowest setting which right now is 80m3/h. Our house is 200m3, so I think that 80m3/h might be a little higher than most people on here seem to have theirs set (I read a lot that people set the normal rate to 0.3ach, which for us would be 65m3/h).

 

I think it's a bit higher because when we set it up in the summer, the house was stuffier and warmer, so wanted as much night-air bypass ventilation as we could. 

 

I've actually added a strange thing but one which I'm really happy with -- a night-time boost lever for the bedroom. It's a three-way valve which we can move so that overnight the bedroom gets air that would normally be going to the (empty) living room, doubling the output without increasing the fan speed. So this might mean that we can turn the normal speed down to 65m3/h.

 

We do definitely need to get a CO2 monitor, this has been on my list for ages! (Right now we're dealing with a floor that's been bodged, the DIY is never done, even when you hire professionals...)

[JohnMo]

3 hours ago, Jolo said:

Our house is 200m3, so I think that 80m3/h might be a little higher than most people on here seem to have theirs set (I read a lot that people set the normal rate to 0.3ach, which for us would be 65m3/h).

We are similar sized I have mine down to 0.3ACH, almost never have to boost for anything. It just 24/7 at the same rate. In summer we have windows open when we fancy (bedroom is window open all summer). Lounge will go high co2 but only if we have about 8 to 10 people in there. Again I will open the window, as it starts to get hot in there anyway.

 

Your 3 way valve will actively encourage more more noise as the flow rates increase locally. So may be not the best solution for noise.

[Jolo]

I should add for clarity, it was always silent in the bedroom on the lowest setting -- the audible hum was when turning it up in the summer, when we wanted to do to get as much cool night air in as possible, i.e. bypass mode on with no heat recovery. Adding the attenuator before the vent meant that we could increase the speed without adding any noise.

 

14 hours ago, JohnMo said:

Your 3 way valve will actively encourage more more noise as the flow rates increase locally. So may be not the best solution for noise.

I did wonder about that too, although the valve itself is 125mm internally, so although it adds a couple of extra bends, the speed within it should be fairly low. It doesn't seem to have added any extra noise, anyway. Even running on higher settings it's silent in the bedroom (even on boost it's only just audible) which was my main goal.

 

With the 3-way valve set to "bedroom boost" we get about 40m3/h into the bedroom (which I think is what PH guidelines suggest), while the system remains set on the lowest speed.