MVHR installers or alternatives?

[Eastfield]

12 hours ago, G and J said:

I’m not sure I agree that it’s impossible to calculate a payback for the cost of MVHR because using Jeremy’s spreadsheet our heating requirement is a lot less than half of what it would be with sub one air changes per hour compared to say five air changes per hour that you’d need with a non-heat recovery system.

 

However, the extra spend to get airtight would be quite difficult to calculate and indeed we’ve not done a cost benefit calculation in payback terms, we’ve gone for it just as an act of faith for comfort.  So despite it being theoretically possible, I think calculating payback for MVHR for us at least is rather pointless. 

Excuse my ignorance, but why do you need such a higher number of changes per hour with a non-heat recovery system?

[G and J]

I think you need a certain number of air changes per hour to keep all fresh.  
 

With trickle vents it’s a blow through.  But with MVHR one still (as I understand it) get a good flow through if fresh air.  
 

It at first appears confusing that we have a really low air change score to make MVHR worth having, but that’s a test of the leakiness of the house, not the number of air changes that a good ventilation system will give. 

[Bonner]

10 hours ago, Eastfield said:

I'm intrigued by your sub £2k system Bonner. Are you willing to share some details? Also, I couldn't agree more re trickle vents, and I do want to have full control of my ventilation.

 

I don't want to compromise on health and comfort, ventilation is not optional. The point Jeremy is making, if I understand correctly, is that the heat saved by the MVHR is not substantial, and it would be more efficient to remove the stale air along with its heat, bring fresh air into the house and heat it via an economical heating method, which I believe I have in the biomass boiler.

Please see another post here, note the unit was 20% cheaper when I bought it. I agree the heat saving is not huge, however you would still need the fan(s), distribution system and method of preheating the incoming air to avoid cold drafts.

 

[JohnMo]

10 hours ago, Eastfield said:

Excuse my ignorance, but why do you need such a higher number of changes per hour with a non-heat recovery system?

You don't but the high number is an instantaneous air flow rate for intermittent fans. Or maybe a house leakage rate at 50Pa, which isn't the actual air movement through a building.

 

You can have good controlled ventilation without MVHR. MVHR is the icing on the cake, when you have done, wall, floor and roof insulation to death, triple glazed and made house airtight. Most houses don't need it, don't benefit from it. But they do benefit from a well thought out and appropriate ventilation system.

[Eastfield]

On 31/12/2025 at 09:02, JohnMo said:

You can have good controlled ventilation without MVHR. MVHR is the icing on the cake, when you have done, wall, floor and roof insulation to death, triple glazed and made house airtight. Most houses don't need it, don't benefit from it. But they do benefit from a well thought out and appropriate ventilation system.

Ah..... the voice of reason. Our house is a new build so by virtue will be exceptionally well insulated and airtight. we have a 'cheap' source of heating. It's all very well those with MVHR stating they'd never live in a house without it, but have they lived in modern, well insulated home with well designed ventilation but no mvhr by comparison? I'd be keen to hear from anyone who has in order to gain an unbiased view.

 

It's easy to disappear down a rabbit hole. Up until I watched the video in my first post I was dead set on MVHR. The concept makes complete sense, however I have been kept awake at night with the problems of routing ductwork, locating the unit and coming up with £5-6k to pay for it. I still need to find a decent company to give me some unbiased and impartial advice, any suggestions would be gratefully received.

 

Thanks for all your responses. We may end up with MVHR yet, but all options will be explored....

[JohnMo]

30 minutes ago, Eastfield said:

so by virtue will be exceptionally well insulated and airtight

Big assumption there, it certainly may not be airtight - unless it was tested to show it is.

 

[saveasteading]

I have awarded hearts to people I agree with.... which is contrary to good logic of listening to all views.

 

But my prejudice, or is it exierience and intuition, is that mvhr is grossly over-rated.

 

We build to control air leakage, then pressure test at high pressure with all fans and vents sealed.

Then we remove the seals and allow draughts to flow freely from each wc and kitchen. Unless they have automatic shutters but they seem rare.

 

Stuffiness can only raise from habitation, but then the fans are used which draw air from everywhere, to be replaced by whatever leakage there may be. Nobody suffocates. 

 

I've only had old draughty houses but the steading (family owned) has no mvhr and has no issues of stuffiness or condensation. I promise to report if that changes.

In business I did  no homes, but offices, nursing homes and school classrooms* would have the same issues..in all cases we agreed with the client to "chance it" without mvhr.... no problems reported ever. That's x 20 applicable  projects at a guess.

So I think I'm right. Still listening of course, but we don't intend to fit £20k on mvhr at the current project.

 

* This seems extreme, with 30+ kids in a room. High ceilings help of course but window vents and door openings appear to suffice.

Perhaps the teachers open windows sometimes.

 

 

[Tony L]

1 hour ago, saveasteading said:

We build to control air leakage, then pressure test at high pressure with all fans and vents sealed.

Then we remove the seals and allow draughts to flow freely from each wc and kitchen. Unless they have automatic shutters but they seem rare.

 

I’m just trying to understand this.  When you say, “We build…”, are you talking about your buildings that don’t have MVHR, or are you talking about people that self-build with MVHR?  Or perhaps both groups of people.

 

My understanding is, if I build a house with MVHR, I would most likely not have vents sucking air from the kitchen & bathrooms straight through my wall to the outside; the bathrooms will just have MVHR extracts & the kitchen will have the same + a recirculating hood over the hob that filters the air rising from the hob then dumps it into the kitchen to be taken away by the kitchen’s MVHR extract port.  Have I got that wrong?

Edited 1 hour ago by Tony L

[Bramco]

4 minutes ago, Tony L said:

Have I got that wrong?

No.

 

Except delete the words 'most likely in the 1st sentence of the 2nd para.

[Tony L]

Thanks for a quick answer on that one, @Bramco. I am just in the process of reviewing/correcting the first draft BC/construction drawings my architectural technician has drawn up for me, & my instructions include a note to delete the MEVs he's drawn in, so I just wanted to be sure.  

[JohnMo]

21 minutes ago, Tony L said:

Thanks for a quick answer on that one, @Bramco. I am just in the process of reviewing/correcting the first draft BC/construction drawings my architectural technician has drawn up for me, & my instructions include a note to delete the MEVs he's drawn in, so I just wanted to be sure.  

If you are doing MVHR you really need an airtightness better than 3.  Otherwise there's a good chance you are wasting energy not saving it. If you are not aiming for level of airtightness there are better or more effective ways to ventilate.

 

There is no reason to have any vents in windows or anywhere else and still be fully compliant with building regs if you are using MVHR.

[Tony L]

Thanks @JohnMo.  My brief to the arch tec specified MVHR & said, “Airtightness will be to near passive standard: we’ll aim for 0.6 & see how close we can get.  Insulation will NOT be to passive standard…”.

 

The arch tec’s drawings include a note which says, “The measured air permeability should be no worse that [sic] 10m3/(h.m2) at 50p.a”.

 

& yes, I understand his 10 is not the same unit of measurement as my 0.6 ACH, but his 10 is too leaky to even meet current building regs for a non-MVHR new build, so this is pretty disappointing, really.  I’m having to request loads of corrections like this.  It’s taking forever.

[Tony L]

Anyway, that’s enough whinging from me, & I don’t want to hijack @Swampy's thread, so can anybody help with @Swampy's request from the first post?

 

 

On 02/02/2024 at 00:28, Swampy said:

If anybody could recommend an MVHR installer local to east Berkshire, that would be great.