MVHR - So many options, how to choose?

[build_a_bear]

Hi, 

My architect has specified an MVHR for our new build property and sold us on the benefits of airtightness and controlled air quality improvements. The property is 5 bedroom and just under 300m2 over two stories.

We've had quotes ranging between £7000 and £21,000 for a variety of units including: 

• Zehnder ComfoAir Q450
• Sentinel Kinetic Highflow
• Airflow Adroit
• Pichler LG350
• Zehnder Comfosystem Q350

with various different options for ducting (radial, rigid, semi-rigid).

 

Our absolutely top priority is that we don't want to hear the thing - at all. We are particularly sensitive to white noise, so it needs to be 100% quiet (or close to). We've also heard horror stories of the ducting being like a secret talk-to-talk system between rooms, which we also do not want.

 

Some of the quotes have included up to £7000 for installation (excluding commissioning), whereas out builder feels like he could probably make a decent job if given a design and some instructions.

 

I'd be grateful for any advice - how can we make sure that we get something that is both affordable and also that is going to perform (i.e. be silent)?

[jack]

10 hours ago, build_a_bear said:

Some of the quotes have included up to £7000 for installation (excluding commissioning), whereas out builder feels like he could probably make a decent job if given a design and some instructions.

 

Bloody Nora that's a ridiculous amount of money, even if commissioning were included.

 

We had our electrician wire our MVHR unit in (literally just a single circuit with appropriate RCBO), and had the plumber install the appropriate drain (again, very little work). My wife and I installed the manifolds and ducts ourselves. From memory, it was basically two easy days of effort.

 

For the £7k quote, even two guys at £350 a day (a ridiculously high day rate) would suggest 10 days onsite, which seems crazy.

 

I doubt that your builder will have any difficulty.

 

11 hours ago, build_a_bear said:

Our absolutely top priority is that we don't want to hear the thing - at all. We are particularly sensitive to white noise, so it needs to be 100% quiet (or close to).

 

That's an unusual problem to have. Unless it's very high volume, white noise (and other random noise types - pink, etc) tends to quickly fade into the background for most people. It's usually more intermittent or repetitive sounds that cause problems. Even ordinary window vents surely let in far more objectionable noise than any decent, properly installed MVHR unit will cause?

 

Nevertheless, noise shouldn't be an issue with a suitable unit, properly installed.

 

We've been running a Brink Excellent 400 for the last 7 years. It's very quiet. We tend to run it well below the calculated building regs rates, which are massive overkill. At those rates, it's completely silent, to the point that I can't tell it's even running unless I stick my ear right near the duct. 

 

Passivhaus-certified units tend to be more expensive, but on average are likely to be quieter than non-certified units. I seem to recall that the Passivhaus Standard places restrictions on the noise output of MVHR units. 

 

The two main sources of noise in rooms with ducts are fan noise and moving air. You can reduce the former by including silencers between the MVHR unit and manifolds. You can reduce the latter by making sure airspeed in the ducts is kept low. This can involve, for example, doubling up duct runs and using larger inlets/outlets (e.g., long slots instead of the small "mushroom" type), which will reduce the noise of air entering/leaving the room.

 

Make sure that outlets in places like the bedrooms (where you're likely to be more aware of noise) are as far from the bedhead as possible.

 

We do currently get a little bit of noise from the unit itself. The fans, in particular, are starting to make a small amount of noise after 7 years of continuous use, and I wonder whether the bearings need replacing. Careful siting of your unit will help mitigate the impact of the small amount of unavoidable noise generated by the unit.

 

11 hours ago, build_a_bear said:

We've also heard horror stories of the ducting being like a secret talk-to-talk system between rooms, which we also do not want.

  

I've heard rumours of this too, but I suspect they're more related to wide-bore branched (rigid) systems that are more typical with American ducted heating and aircon than with the radial systems installed with most MVHR units these days. I don't recall anyone on BuildHub reporting this, despite a large number of us having installed MVHR in our houses. Perhaps avoid the rigid systems is you're really concerned about this.

[Nickfromwales]

Radial will get you as close to silent as possible. Series creates cross talk, and requires huge ducting at the start of the system in comparison.

I use Brink and have reports of “complete inaudibility” with attenuators at the unit and airflow managed by design, to compliment. 
On 2 installs currently using the Brink Flair + main units, plus Brink Air Comfort units for post heating and cooling

Fantastic results on my previous passive ( airtight ) projects, all using Brink, and that’s all I use these days tbh. 
 

Prices for your install should be a bit above the midrange of what you’ve been quoted, but spec / design will dictate the final price. 

[SteamyTea]

46 minutes ago, jack said:

don't recall anyone on BuildHub reporting this, despite a large number of us having installed MVHR in our houses

Ask @joe90 I think he had this problem.

[Nickfromwales]

 

[Blooda]

4 hours ago, jack said:

Perhaps avoid the rigid systems is you're really concerned about this.

 

Ours is rigid, and we don't have that problem, but doing it again would use radial, as it seems easier to install. 

[joe90]

7 hours ago, SteamyTea said:

Ask @joe90 I think he had this problem.

Nope, sorry mate, mine is virtually silent (you have to listen hard to hear slight air movement noise unless on boost) 

7 hours ago, Nickfromwales said:

Radial will get you as close to silent as possible.

+1, and I made my own manifold and lined it with acoustic foam to act as a silencer as well, also the flow adjusters are at the manifold not the outlet into the room (these can create noise as they are throttling the air in the room)

[Jenki]

3 hours ago, joe90 said:

I made my own manifold and lined it with acoustic foam to act as a silencer as well, also the flow adjusters are at the manifold not the outlet into the room (these can create noise as they are throttling the air in the room)

any photos / details of your DIY manifold and flow adjusters? please

[joe90]

Edited November 11, 2022 by joe90

[joe90]

Flow adjusters are real Heath Robinson but they work, 

[Jenki]

thanks for the picture @joe90👍.  Love it, Heath Robinson or not, if it works and saves some money I'm in...

 

@joe90 - hanging from the roof do you get any resonance?

Edited November 11, 2022 by Jenki

[SteamyTea]

3 minutes ago, Jenki said:

hanging from the roof do you get any resonance

I can answer that, having been imprisoned in @joe90's attic.

No.

 

You may have noticed that his loft is a warm roof, and I think he sucks some of the warmth out of it, as well as the rooms.

[crispy_wafer]

25 minutes ago, SteamyTea said:

You may have noticed that his loft is a warm roof, and I think he sucks some of the warmth out of it, as well as the rooms.

@joe90 Like placing an extract vent (like bathroom & kitchen) to capture the warmer air?

[SteamyTea]

2 minutes ago, crispy_wafer said:

@joe90 Like placing an extract vent (like bathroom & kitchen) to capture the warmer air?

Yes, most of the time a loft, even an uninsulated one, gets quite warm.  Also helps the ventilation: a warm roof is, but definition, really just another room.

[joe90]

11 hours ago, Jenki said:

@joe90 - hanging from the roof do you get any resonance?

None, hung from roof so not connected to ceiling joists, also on rubber feet.

11 hours ago, SteamyTea said:

You may have noticed that his loft is a warm roof, and I think he sucks some of the warmth out of it, as well as the rooms.

Yes, I had a spare extract so ran it up to the ridge within the warm roof.

11 hours ago, crispy_wafer said:

Like placing an extract vent (like bathroom & kitchen) to capture the warmer air?

Yes

11 hours ago, SteamyTea said:

can answer that, having been imprisoned in @joe90's attic.

Don’t read anything into that 😱, he was installing his monitoring kit , honest 😇

[Dave Jones]

On 11/11/2022 at 07:52, joe90 said:

 

must be great breathing in all those particles of perished rubber around the lid.

 

Crazy to bodge and skimp on a couple hundred quid manifold ...

[build_a_bear]

Thanks for the advice. To summarise if I may:

• Radial ducting should avoid most of the noise and potential for cross-talk
• £7k for installation is far too high
• Put flow adjusters by the manifold.

I guess a couple of specific questions:

1. I know the Brink gets rave reviews here, anyone with any experience +ve or -ve of the Zehnder or VentAxia?
2. With radial do you still need silencers on each run?
3. Any downsides or bear traps I need to be aware of?

Thanks again!

[Russdl]

@build_a_bear 

 

1. Sorry, can’t help with alternatives as we’ve got a Brink but there are negatives to the Brink from my point of view. All the good stuff is good but the app is poor as is web access - all seems a bit last decade, but not a game changer, hardly ever need it. 
 

2. No. A silencer before the manifold should suffice. The manifold has baffles that help as well - not 100% effective on a quiet night, maybe 95% but that’s subjective. There will be a tiny bit of ‘white noise’ but you’ll have to try hard to hear it. 
 

3. Don’t pay too much for it. Can you DIY the pipes? A day of fun and save a fortune?

[jack]

10 hours ago, build_a_bear said:

1. I know the Brink gets rave reviews here, anyone with any experience +ve or -ve of the Zehnder or VentAxia?

 

Not sure about the Zehnder, but I'm sure several members have installed VentAxia units. Google "vent axia buildhub" and you'll get loads of info. You could try the same with Zehnder. 

[Dave Jones]

went for Zehnder Q350 with a Comfopost CW6 cooling unit for heat pump cooling in the summer.

[boa72]

Hi all,

 

you can have a look at this blog https://vmcdoublefluxblog.wordpress.com/ if you want some interesting information about MVHR. There is a comparison between a lot of different brands.