MVHR ? Who needs it? I don't.

[ToughButterCup]

Well yes OK, for sign off I do.

But Hell, after 4 years without MVHR ( first fit already done) - and now for the first time able to afford the box (second fit) .... I'm feeling like its a waste of money. Well if not a waste, then I begrudge the money.

Doors and 3 meter slider open April to September. I think I might only be using it for three or at thee most 4 months of the year.

 

Grrr. I know, I know.  😑

[nod]

100% agree Ian 

Like having air con in a convertible 🚗 

[IanR]

  On 09/04/2025 at 08:40, ToughButterCup said:

.... I'm feeling like its a waste of money. Well if not a waste, then I begrudge the money.

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Are you able to measure CO2 levels in your house?  The BC requirement for mechanical ventilation when you are under 3m³/m².h@50Pa infiltration is a really rough proxy air quality. For your own benefit it would be better to know the CO2 levels without MVHR and if it goes above 1,000 ppm then you'd be better off having MVHR, and if above 2,000 ppm it would be a health risk not to have MVHR.

I've tried running without the MVHR on between Spring and Autumn, and I don't like bathrooms not drying out as quick as I've got used to, even with a small window open...

[Nickfromwales]

Do you then just waft the stench of a #2 around with a dinner tray? And dry the walls of the bathroom with a towel?

 

MVHR is exactly that, for the times where the house cannot be left open to the elements, at winter, and at night for ground floor at least for security, plus any time you are away. It costs next to nothing to run and provides heat recovery, so utter madness to not use it, more so to make a high performance dwelling and then not complete the circle by having the heat recovered vs letting it blow out to the clouds.

 

  On 09/04/2025 at 09:08, nod said:

100% agree Ian 

Like having air con in a convertible 🚗 

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Have you got extractor fans in all your bathrooms which you never ever use? 🙄

[Redoctober]

  On 09/04/2025 at 08:40, ToughButterCup said:

Well yes OK, for sign off I do.

.... I'm feeling like its a waste of money. Well if not a waste, then I begrudge the money.

 

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Needed for sign off ! How close to the threshold were you? I have known people who have "been allowed to leave a gap" somewhere in order to raise the figure in their favour.

 

But that said, your feeling has hit this debate square on the head. It does carry weight though, as you have lived without such a thing for a good few years and one could argue, your lifestyle hasn't been affected by it not being in your life. 

 

No one can really argue against the benefits of such a system, it boils down to whether or not the individual considers it a worthy investment, on balance. 

[ProDave]

If you have done first fix and fitted all the vents and ducts, then you have bought and installed the expensive bit.  I found the actual MVHR unit cost less than the ducting  so you might as well buy it and fit it.

 

For a good portion of the year we sleep with the bedroom window slightly open, but that won't ventilate the whole house so we leave the mvhr on.

[ToughButterCup]

  On 09/04/2025 at 09:26, IanR said:

Are you able to measure CO2 levels in your house? ...

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Yes.

I measure the  CO2 levels constantly. I move the monitor around and peek at it now and then.

This is in the office right now. I hardly ever look at the numbers: I look at the light. Yes, on occasion its red.

 

  On 09/04/2025 at 09:55, Nickfromwales said:

Do you then just waft the stench of a #2 around with a dinner tray? 

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Ooop North we don't fuss about stuff like that . A wide open window sorts that out during the #2 process. Saves on Fart Spray too.

 

  On 09/04/2025 at 09:55, Nickfromwales said:

...And dry the walls of the bathroom with a towel? ...

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Large windows in each bathroom. Open for a few minutes. I've hidden the bathroom windows behind cladding (with 12mm gaps) so the windows can be wide open - so our cheeky bits are hidden .

 

  On 09/04/2025 at 09:55, Nickfromwales said:

...

MVHR is exactly that, for the times where the house cannot be left open to the elements, at winter, and at night for ground floor at least for security, plus any time you are away

...

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Exactly right.

In any wind and rain direction we always have a down-wind window:  mostly there's one window open. But, on occasion all the windows are indeed closed. When I'm away, well, I just don't care .....

But you are right, there are a couple of nights when we don't have our bedroom window wide open. Our Wintergarden roof overhangs the bedroom window by 3 meters, so our room is protected under that and some large vertical louvres.  What Kevin WhatHisFace calls a Breeze Corridor.

 

Folks, I'm just feeling mean. I know MVHR is  A-Good-Thing. Well, I'm told it is😜

 

Call it Concerned  Impecunious Old Age.

[Iceverge]

It's entirely possible that MVHR isn't the optimum solution for you. 

 

I'm going to make some wild (and inflammatory😈) assumptions here. 

 

1. You are a couple of 900 year old geriatrics rattling around in a huge house. 100m2 plus each to allow your dusty farts to dilute hugely and waft harmlessly into the curtains. 
2. You prefer to take a long sedentary steam free bath for your "bones" rather than a rapid steamy shower like those of us who have actual work to do. 
3. As you were born in the 1800's you still follow the daily routine of opening every window in the house just like your childhood chambermaid used to do to dispel the "pot gasses". 
4. You enjoy burning lumps of timber almost as much as you treasure the opinion pages of the Daily mail and mid afternoon TV with reruns of 1960's dramas. 
5. You suspiciously view an MVHR unit as "too good to be true" and treat it accordingly and think a much more decent, and honourable thing to do, is pay old fashioned British Gas an honest wage and not to cheat the system. 
6. You have lots of lots of Sterling silver and Kruger Rand still buried under the bed from when you were forced to sell the last of your slavery bonds by the "WOKE" government. Spending another token or two on the boiler churning through some of Putins gas isn't going to make a dent in the intergenerational wealth. 

 

 

You asked........I poked..............

 

( actually that reminds me of my first GF.....)

 

 

 

 

 

[ToughButterCup]

  On 09/04/2025 at 11:25, Iceverge said:

...

1. You are a couple of 900 year old geriatrics rattling around in a huge house. 100m2 plus each to allow your dusty farts to dilute hugely and waft harmlessly into the curtains. 
2. You prefer to take a long sedentary steamy bath for your "bones" rather than a ...
3. As you were born in the 1800's you still follow the daily routine of opening every window in the house just like your childhood chambermaid used to do to dispel the "pot gasses". 

...

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Re 1:

I time my farts for bath time. Blowing bubbles is my one totally innocent pleasure : Debbie has had to remind me that the sound insulation between the floors is not good enough to do that when we have guests

Re 2:

Now that Mr Stewart has given me two brand new hips I'm back into having baths. Bath for increased blood supply to the new bits of metal and ceramic followed by a very hot shower

Re 3: 

Bang on. The German ...luften... ( to blow the room through with clean air ) is hard-wired. My Berlin- based family is still doing it , mind you there's a massive (wood and - if you can get it-  brown  coal fired ) tiled furnace in the cellar. The chimney sweep signs it off every year as emissions compliant [It isn't] . Its hotter than the engine room on a Clyde Puffer.

 

 Re 5+6 , wellllll.....

[G and J]

  On 09/04/2025 at 09:08, nod said:

100% agree Ian 

Like having air con in a convertible 🚗 

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Having had two convertibles I think k aircon is vital.  They are buggers to dry out in cold times of the year otherwise. 

[Mike]

  On 09/04/2025 at 12:07, ToughButterCup said:

Bang on. The German ...luften... ( to blow the room through with clean air ) is hard-wired. My Berlin- based family is still doing it

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Yes, recently-build German homes are underperforming by between 15 to 35% compared to their expected energy performance because of that!

 

Its a major factor preventing Berlin (and Germany) from achieving its energy efficiency targets: Germany’s inefficient love affair with open windows - Politico

 

Seems like they need to keep their windows shut more often (or use Stoßlüften) and lean to love MVHR

 

 

Edited April 9 by Mike

[ToughButterCup]

Thanks very much for the link. Really interesting

[Iceverge]

  On 09/04/2025 at 23:08, Mike said:

Yes, recently-build German homes are underperforming by between 15 to 35% compared to their expected energy performance because of that!

 

Its a major factor preventing Berlin (and Germany) from achieving its energy efficiency targets: Germany’s inefficient love affair with open windows - Politico

 

Seems like they need to keep their windows shut more often (or use Stoßlüften) and lean to love MVHR

 

 

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Come to Ireland where people love to turn off the bathroom extractor, dry a week's washing in the living room and bolt every orifice of the envelope closed.

 

A smoky oil boiler is fired intermittently, never long enough to warm the house but just enough to take the relative humidity below 100% momentarily to allow the air to absorb even more damp that instantly gets redeposited behind the curtains. 

 

The mould on the plaster gets so thick you can't tell where the carpet ends and the wall begins. 

 

As condensation waterfalls down the windows, the witless inhabitants phlegm cough and complain about the rain making it's way through the walls again. 

 

Give me "Luften" any day .......

[Bonner]

Another vote for MVHR here, this is my inlet pre-filter after a month! We are in a rural village so probably a combination of wood burner smoke and agricultural dust. Anyway I prefer not to let fresh air in the house. 

[SteamyTea]

  On 12/04/2025 at 09:25, Bonner said:

agricultural dust

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It is quite a problem.

Maybe farmers need to contribute more in taxes to counteract the environmental damage they can do.

[NSS]

We never open windows. In fact, but for the requirement to have openers for means of escape, we could have saved a bundle by having all fixed panes.

 

After 7.5 years living with MVHR, I can't imagine ever going back to living without it.

[JohnMo]

  On 12/04/2025 at 20:47, NSS said:

We never open windows

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We open ours quite often, living room and bedroom windows been open all day, bedroom been open for the last few weeks.  But heating is off (or what heating we have on is powered by PV) so not saving or loosing anything.

[Pocster]

I find mvhr invaluable.

zero mould / moisture issues 

air is fresh 

 

also ; look at the pollution removed …

[SteamyTea]

  On 13/04/2025 at 07:10, Pocster said:

also ; look at the pollution removed …

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That is the air exiting your dungeon though.

[Pocster]

  On 13/04/2025 at 07:13, SteamyTea said:

That is the air exiting your dungeon though.

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Nah that’s the air intake 

[Garald]

Just learned that the way Canadian wells are rated in France for energy-rating purposes is 'pretend the user has MVHR'.

 

(What do they do if someone has both? Report him as an overachiever?)

[ToughButterCup]

  On 10/04/2025 at 18:37, Iceverge said:

...

Give me "Luften" any day .......

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And let the smog-filled air into your Berlin high-rise ?

There's a standing joke in Berlin ... Stossluften (shock ventilation) is really about neighbours being able to chat to one another:

 

Old Mother Schmidt opens her window wide, puts a cushion on the window shelf, and hoists her décolletage onto a longsuffering  cushion, bangs on her neighbours window.

Frau Dumke (old Berlin name) opens her window, stands on a chair, sticks hers out of the window too : both of them put the world to rights.

I'll spare you the teenage jokes about that process.

 

 

No wonder they cant use MVHR properly. They open the window to talk to one another. Not because their flat is chock full of sauerkraut and the consequent farts.

[MikeSharp01]

  On 13/04/2025 at 07:10, Pocster said:

 

also ; look at the pollution removed …

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You are allowed to wear your boots in the house -  🫡 

[Oz07]

what levels do you get up to in bedrooms at night? Do you have windows cracked? Think winter is where it saves the money. I generally agree that the benefits are oversold, probably because when we have spent thousands on it we are not always honest with ourselves. That being said I would always put one in another new build.

[JohnMo]

  On 19/04/2025 at 06:16, Oz07 said:

That being said I would always put one in another new build.

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If I did it again (unlikely) I would just do demand based MEV. Humidity control trickle vents, humidity control wet room terminals and automatic speed control on the MEV unit.

 

No filter to change, one fan, only running when actually required and only in the area needed.