MVHR is Largely Bogus

[Mike]

11 hours ago, coconutsaregood said:

Just noting your assertion on one of the several group of pollutants: VOC. A failure to limit this problem alone implies the chosen ventilation system is not complying with the current bldg regs

The building regulations set only set the minimum standards for ventilation, and it's more-or-less accepted that those standards are fine for day-to-day living if the users use them properly. If the turn off the MVHR, don't change the filters, close off the trickle vents, don't open windows, etc, there will be a problem - and that's more likely in poorer households where people struggle to pay for heating.

 

However a new house may or may not have a VOC problem, depending on the products chosen, particularly during the the first two to three years. I have seen a study on this but don't have the details. At the moment, in the UK, there's not even much awareness of the issue.

 

France, in contrast, has had a mandatory labelling scheme for key construction and decorating products since 2013, linked to the levels of 10 key VOCs, plus the voluntary 'intAIRieur' auditing scheme for the indoor air quality of new housing.

 

Since you have time for research, you may want to check out the Natureplus database (an Austrian initiative, so mainly Austrian / German products) and the USA Healthy Building Network and Healthy Materials Lab. Plus the work of the UK Green Building Council and Alliance for Sustainable Building Products.

 

Edited March 24, 2020 by Mike

[Russell griffiths]

I have read a couple of posts on this, haven’t read them all life’s too short. 

But my thoughts are why does something have to add up money wise, if you think it will improve your home environment why does it have to add up that it equals out what it costs. 

 

Do you never ever go to a restaurant and think I would really like the big 24oz T bone steak, but it’s £29 and the 6oz burger is only £12 do you buy the burger because it represents better value or do you want a steak. 

 

I dont understand the comments of my MVHR cost £3000 but it saves me x from my heating, who gives a toss, from everybody on here who has it I haven’t seen anybody who regretted it, if it makes for a good living environment who cares what it costs. 

[Redoctober]

2 hours ago, Russell griffiths said:

I have read a couple of posts on this, haven’t read them all life’s too short. 

But my thoughts are why does something have to add up money wise, if you think it will improve your home environment why does it have to add up that it equals out what it costs. 

 

Do you never ever go to a restaurant and think I would really like the big 24oz T bone steak, but it’s £29 and the 6oz burger is only £12 do you buy the burger because it represents better value or do you want a steak. 

 

I dont understand the comments of my MVHR cost £3000 but it saves me x from my heating, who gives a toss, from everybody on hear who has it I haven’t seen anybody who regretted it, if it makes for a good living environment who cares what it costs. 

 

Fair comments but the life I lead isn't like that sadly. I'm not in a position whereby I can dismiss the cost of any such item and I'm sure I am not alone. God forbid if I purchased everything I fancied / that was better for me etc without any regard to the costs / value, I'd be living under the hedge rather than admiring it from my comfy armchair!!?

[newhome]

49 minutes ago, Redoctober said:

Fair comments but the life I lead isn't like that sadly. I'm not in a position whereby I can dismiss the cost of any such item and I'm sure I am not alone. God forbid if I purchased everything I fancied / that was better for me etc without any regard to the costs / value, I'd be living under the hedge rather than admiring it from my comfy armchair!

 

True, but people place value on different things based on how important something is to them. For some a kick arse tool is of great importance, others have horses, designer handbags, flash cars et al. You can buy cheaper versions of all of those things (well the horse might be a cat instead ? ) but ultimately we all place different values on things. From the comments here it would seem that many people believe that MVHR is worth it for the air quality alone whereas others would be quite happy with trickle vents. It doesn't make one view invalid - vive la difference. 

 

[Jeremy Harris]

Every self builder makes choices as to what they choose to spend a bit more on, and what they choose to spend a bit less on.  Some opt for fairly expensive external finishes, or front doors that cost as much as an MVHR unit, some opt to pay more for a plot because the location is worth it for them.

 

For us it was very much "fabric first", getting a house that needed as little energy to run as possible, so we were prepared to invest more in the basic fabric in order to reduce energy use (and running cost) through life.  MVHR was one of those choices made to reduce energy use, but having lived with it for a time we both now think that the energy saving is the least important feature of having MVHR.  The air quality is just so much better than any house we've ever lived in that we'd have it even if it didn't reduce the heating bill a bit.  That's not something that would have initially driven our decision to install it, though.

[MikeGrahamT21]

On 28/03/2020 at 13:47, Russell griffiths said:

I have read a couple of posts on this, haven’t read them all life’s too short. 

But my thoughts are why does something have to add up money wise, if you think it will improve your home environment why does it have to add up that it equals out what it costs. 

 

Do you never ever go to a restaurant and think I would really like the big 24oz T bone steak, but it’s £29 and the 6oz burger is only £12 do you buy the burger because it represents better value or do you want a steak. 

 

I dont understand the comments of my MVHR cost £3000 but it saves me x from my heating, who gives a toss, from everybody on hear who has it I haven’t seen anybody who regretted it, if it makes for a good living environment who cares what it costs. 

Exactly!

 

Its not only the tangible benefits of MVHR, but also the intangible which makes it such a relevant technology.

[Levo]

I am about to install an MVHR. All kit ready, waiting for marginally warmer weather.

The reasons for my installation are:

1- Pollen filter to help cut down on my son's Hay Fever.

2- Air quality. I suggest people invest in a CO2 monitor and check the levels in a couple of rooms. You would be amazed how quickly it goes to red without ventilation. Trickle vents would bring cold (bitter cold these days) air in and I hate the cold air flow. Example: TV room ~23m2. Begin at 400-500, two people watching TV, 2-3 hours later in red (1200+). CO2 PPM below 800 is deemed good, above 1200 it is bad and it is acceptable in between. Imagine a similar size or smaller bedroom with 2 people sleeping for 8 hours.

3- It will reduce the gas usage somewhat. I mention this not from cost perspective but environmental angle. Some may argue that the CO2 cost of manufacturing etc probably outweighs this.

I live in a 1970s detached house. It does have some gaps here and there which I will need to plug but the important rooms are reasonably airtight, so I am hoping it will serve to increase the air quality and remove the need to open windows and causing cold drafts and therefore providing better comfort.

Looking at this purely from cost perspective is wrong in my opinion. Anybody who does, I assume (as an example) has no TV in their house as one can argue a TV provides 0 £ value, and is therefore just cost...so impossible to justify.

Edited December 30, 2020 by Levo

[SteamyTea]

12 hours ago, Levo said:

Looking at this purely from cost perspective is wrong in my opinion. Anybody who does, I assume (as an example) has no TV in their house as one can argue a TV provides 0 £ value, and is therefore just cost...so impossible to justify.

Dead right.  I cannot see any value in swapping my cheap kitchen counter top to an expensive granite one, but people still do.  And I bet I can cook better than most of them.

[Redoctober]

21 hours ago, Levo said:

Looking at this purely from cost perspective is wrong in my opinion. Anybody who does, I assume (as an example) has no TV in their house as one can argue a TV provides 0 £ value, and is therefore just cost...so impossible to justify.

 

mmm. The word "value" complicates your arguement I feel. How can you or indeed anyone, say that a TV [for example] couldn't be "most" valued thing in someones life and therefore justified?

Making any decision to purchase any item has to be considered carefully. Such as house building - It depends what one is building for. Is it to sell on for profit in the very near future or indeed next few years? Is it a forever home? These are the sort of considerations one has to be mindful of when purchasing anything I would argue. So you are right to say that looking at it from a cost prospective alone, is wrong but in that equation one has to consider "value" and "justification"  

[Bitpipe]

8 minutes ago, Redoctober said:

 

mmm. The word "value" complicates your arguement I feel. How can you or indeed anyone, say that a TV [for example] couldn't be "most" valued thing in someones life and therefore justified?

Making any decision to purchase any item has to be considered carefully. Such as house building - It depends what one is building for. Is it to sell on for profit in the very near future or indeed next few years? Is it a forever home? These are the sort of considerations one has to be mindful of when purchasing anything I would argue. So you are right to say that looking at it from a cost prospective alone, is wrong but in that equation one has to consider "value" and "justification"  

 

The common business calculation for determining 'value' is Return On Investment.

 

ROI=(Net Return  on  Investment/Cost  of  Investment)×100%

 

My MVHR system cost me about £4k and I self installed. Given I needed a ventilation system to meet BR so you could subtract, say £500 for decent external extractor fans for each bathroom and the kitchen and some means to ventilate the basement. Then I'd have needed trickle vents for the windows (given mine were passive, not an option) but lets assume I could get them for another £500 as an optional extra.

 

So now I'd need to model the heat loss incurred by traditional ventilation and understand how that impacted my space heating design. It's likely I'd have needed to put heating in each bedroom (currently none) so maybe another £1500 for first floor UFH.

 

So the net cost for the MVHR is £1500.

 

I'd then need to calculate the additional energy cost to heat the house year round (currently its an average of £1/day for gas) and then I could work out the 'saving' factoring in the electric used by the MVHR and consumables (filter etc). I'm not sure you could model the 'fresh air' benefit. Let's say it's a £250 net saving per year in energy cost (assuming no change in energy cost).

 

So assuming the system has a useful life of 15 years, it will save me £3750 so the ROI is 3750/1500 *100% = 250% which is about %16 per year - a decent return.

 

Obviously these numbers would need much more scrutiny but probably not a million miles off.

 

Now, next job is to calculate the ROI for the engineered stairs that have no stringer and look the same from below as above. Doubled our stairs budget but they make me smile every time I look at them - what's that worth

 

 

  

[Gav_P]

33 minutes ago, Bitpipe said:

 

The common business calculation for determining 'value' is Return On Investment.

 

ROI=(Net Return  on  Investment/Cost  of  Investment)×100%

 

My MVHR system cost me about £4k and I self installed. Given I needed a ventilation system to meet BR so you could subtract, say £500 for decent external extractor fans for each bathroom and the kitchen and some means to ventilate the basement. Then I'd have needed trickle vents for the windows (given mine were passive, not an option) but lets assume I could get them for another £500 as an optional extra.

 

So now I'd need to model the heat loss incurred by traditional ventilation and understand how that impacted my space heating design. It's likely I'd have needed to put heating in each bedroom (currently none) so maybe another £1500 for first floor UFH.

 

So the net cost for the MVHR is £1500.

 

I'd then need to calculate the additional energy cost to heat the house year round (currently its an average of £1/day for gas) and then I could work out the 'saving' factoring in the electric used by the MVHR and consumables (filter etc). I'm not sure you could model the 'fresh air' benefit. Let's say it's a £250 net saving per year in energy cost (assuming no change in energy cost).

 

So assuming the system has a useful life of 15 years, it will save me £3750 so the ROI is 3750/1500 *100% = 250% which is about %16 per year - a decent return.

 

Obviously these numbers would need much more scrutiny but probably not a million miles off.

 

Now, next job is to calculate the ROI for the engineered stairs that have no stringer and look the same from below as above. Doubled our stairs budget but they make me smile every time I look at them - what's that worth

 

 

  

Don’t forget ROI should also consider a contingent valuation. This could generate much greater value than just traditional cost savings approach.

[joe90]

1 hour ago, Bitpipe said:

The common business calculation for determining 'value' is Return On Investment.

but unless your building a house to sell on it’s not a business. I installed MVHR for quality of life, I have a tv because I like it and can afford it. I don’t have granite worktops because I think they are massively overpriced (and not that easy to look after/based on kitchen installation fir years and hearing from customers). I am always surprised by people having new range Rovers on the drive but living in a pokey terraced house. I would rather have a detached nice house and drive an old Merc (? oh I do). It’s all about life’s choices not necessarily justification. 

[Gav_P]

5 minutes ago, joe90 said:

but unless your building a house to sell on it’s not a business. I installed MVHR for quality of life, I have a tv because I like it and can afford it. I don’t have granite worktops because I think they are massively overpriced (and not that easy to look after/based on kitchen installation fir years and hearing from customers). I am always surprised by people having new range Rovers on the drive but living in a pokey terraced house. I would rather have a detached nice house and drive an old Merc (? oh I do). It’s all about life’s choices not necessarily justification. 

This is exactly what the contingent valuation considers... the harder to measure items that you are happy to pay for. 

[Bitpipe]

35 minutes ago, joe90 said:

but unless your building a house to sell on it’s not a business. I installed MVHR for quality of life, I have a tv because I like it and can afford it. I don’t have granite worktops because I think they are massively overpriced (and not that easy to look after/based on kitchen installation fir years and hearing from customers). I am always surprised by people having new range Rovers on the drive but living in a pokey terraced house. I would rather have a detached nice house and drive an old Merc (? oh I do). It’s all about life’s choices not necessarily justification. 

 

Totally agree, but I was trying to address the more direct 'is it worth it' question from a monetary standpoint.

 

For an existing dwelling, where there is already whole house heating and extraction, then the return would be much lower. Possibly negative as low airtightness would render the heat recovery element negligible.

 

1 hour ago, Gav_P said:

Don’t forget ROI should also consider a contingent valuation. This could generate much greater value than just traditional cost savings approach.

 

Maybe this is what I need for my fancy stairs

[Levo]

19 minutes ago, Redoctober said:

mmm. The word "value" complicates your arguement I feel. How can you or indeed anyone, say that a TV [for example] couldn't be "most" valued thing in someones life and therefore justified?

Hi, I think we are saying the same thing.

I didn't say the TV isn't valuable to someone, as it is definitely valuable to me because I have a large one. Just that it didn't bring back a fiscal value.

[George]

I'm 75% the way through installing MVHR (radial ducting in, just need final runs from manifold and to the roof). Can't switch it on yet as still plodding away on the inside. 

 

I did consider an alternative plan of installing a positive input ventilation in the loft, plus 3No single room MVHR extractors (2x bathroom and kitchen). In hindsight, this probably was a better solution but I am hopeful the whole house system is worth it.

 

ROI is less of a concern due to wanting to resolve damp (normal old house damp, nothing dramatic) and air quality.

[JFDIY]

36 minutes ago, George said:

ROI is less of a concern due to wanting to resolve damp (normal old house damp, nothing dramatic) and air quality.

I don't think you'll be disappointed.

 

My house used to stream with condensation from October to march, we'd get up and wipe all the glass down daily. We only dried one or two items of clothing a week in the house, it drove us mad

 

Since fitting the MVHR, the house is bone dry, probably too dry some days as I now have to put moisturiser on!.

 

We even now dry most of our clothes in the bathroom, with no more than a bit of condensation on the bathroom window for an hour or two as the extract clears it.

 

 

 

[MJNewton]

10 minutes ago, JFDIY said:

I don't think you'll be disappointed.

 

Agree with that. Whilst we never had much of an issue with condensation, I still fancied the idea of MVHR for its general benefits. My wife said recently how quickly our washing is drying (yes, we hang it indoors - that'll never change I suspect) and it was completely unprompted and she hadn't made the connection with the MVHR.

[ToughButterCup]

On 01/01/2021 at 11:16, Levo said:

.... Just that it didn't bring back a fiscal value.

 

Fiscal deficit boys! 

Run for the hills. An economist has infiltrated us.  Arrggghhhh!

[Oldsteel]

In tune with many others here (this thread was started in 2019!) the MVHR was the best thing I installed in my previous self-build - which we finished in 2009 and lived in for 8 years. The original reason to install it was to avoid those awful trickle vents in windows, which as somneone rightly said create a draught in windy weather and dont work when there is no wind. Our system was one of the original Orca systems, with minimal controls. The only problem was the humidity sensors which failed quite quickly and I couldnt get replacement - it semeed to work fine without them though. But it kept the whole house fresh and dry including those rarely-used spare rooms, and other than an annual clean of the filters (and probably a 4 year scrub of the fan blades) it worked well and silently. During hot summers I turned it off as we had windows open most of the time.

It is a prime requirement for our new build starting in April and I am looking forward to improved controls over our previous system. We are currently living in an older house which has no vents at all but is probably porous enough not to need them ?

[Seeoda]

On 19/12/2019 at 16:31, Jeremy Harris said:

 

It's a nasty, wet, day here, and we've been shut indoors all day, not even gone outside once, so all doors and windows have been shut tight since yesterday.  Just taken this 'photo of the hall display from the house monitoring/data logging system:

 

 

That CO₂ level is around 100ppm higher than we normally see, most probably because the MVHR hasn't been on boost since around 08:00 this morning, and because neither of us has been out of the house.  If I started seeing levels as high as 900ppm then I'd be looking to find out why they had risen so high.  We find that the CO₂ level tends to fluctuate between about 450ppm up to about 800ppm, but never much higher than that.  The outside CO₂ level here seems to be about the global normal concentration ~420ppm.

 

 

 

Can you send me the name of that data logger model? Thanks

[Adsibob]

On 18/12/2019 at 23:58, Temp said:

+1

 

Our house is far from airtight. We have two chimneys for starters. Despite this the incoming air from the MVHR vents is noticeably warmer than outside air so we are recovering some energy even if it not optimum.

 

The air quality is far better than any house we have lived in before. My feeling is that this is due to the constant high level of ventilation MVHR provides. Love it.

 

In short I would install one again even if it actually cost me money to run.

 

@Temp I also have two fire places and am thinking of installing MVHR. Which unit did you go for?

[troggy02]

Interesting read, and certainly can't comment on the cost argument, but thought I'd share our experience. We moved in to highly insulated new build one year ago. I'd describe it as a semi-passive house in so far as we can normally maintain around 21c down to about 8-10c outside without heating, and then with very little until it gets towards zero. It's a fairly large property with Samsung 18kW ASHP. We previously lived in a new Persimmons house (and that's a whole other story!).

 

What we've noticed:

• When you walk in to the house, it never has the familiar odour that most homes do. It just smells like the outside.
• My wife's a keen cook. The kitchen is designed without a hood, but any degree of smell in the house clears within an hour completely even though the house is open plan.
• We live in the country but its amazing how many pollutants the filters remove. Especially when neighbours have their log fires lit!
• Anybody with hay fever loves our house. They get instant relief from the moment they enter.
• We don't suffer from cold spots in rooms, or rooms that are a different temperature to others.
• Cloths hung inside dry far quicker than in previous houses. The house humidity is very stable all year round.
• During the summer when it was 35c outside, we were able to maintain 26c in doors with fresh air - heat recovery works both ways of course.
• When the outside temperature drops at night, the MVHR goes in to bypass mode with boost to help remove excess heat from the house. Throughout last summer this was a God send, especially since we get considerable solar gain from our windows.
• I've configured the unit to drop from it's regular 58% to 30% overnight. As others have said, the standard setting is unnecessary over night both from a power and noise point of view.

[Adsibob]

2 hours ago, troggy02 said:

Interesting read, and certainly can't comment on the cost argument, but thought I'd share our experience. We moved in to highly insulated new build one year ago. I'd describe it as a semi-passive house in so far as we can normally maintain around 21c down to about 8-10c outside without heating, and then with very little until it gets towards zero. It's a fairly large property with Samsung 18kW ASHP. We previously lived in a new Persimmons house (and that's a whole other story!).

 

What we've noticed:

• When you walk in to the house, it never has the familiar odour that most homes do. It just smells like the outside.
• My wife's a keen cook. The kitchen is designed without a hood, but any degree of smell in the house clears within an hour completely even though the house is open plan.
• We live in the country but its amazing how many pollutants the filters remove. Especially when neighbours have their log fires lit!
• Anybody with hay fever loves our house. They get instant relief from the moment they enter.
• We don't suffer from cold spots in rooms, or rooms that are a different temperature to others.
• Cloths hung inside dry far quicker than in previous houses. The house humidity is very stable all year round.
• During the summer when it was 35c outside, we were able to maintain 26c in doors with fresh air - heat recovery works both ways of course.
• When the outside temperature drops at night, the MVHR goes in to bypass mode with boost to help remove excess heat from the house. Throughout last summer this was a God send, especially since we get considerable solar gain from our windows.
• I've configured the unit to drop from it's regular 58% to 30% overnight. As others have said, the standard setting is unnecessary over night both from a power and noise point of view.

Thanks @troggy02 thats v helpful. What make and model unit do you have and who did the install and design?

 

Edited January 30, 2021 by Adsibob

[Pocster]

10 minutes ago, Adsibob said:

Thanks @troggy02 thats v helpful. What make and model unit do you have and who did the install and design?

 

I’ve only put my mvhr on once for about 5 hours . Went out , came back - I could feel the difference.