MVHR is Largely Bogus

[Onoff]

7 minutes ago, DavidHughes said:

>onoff

>All the facts, figures, calcs and arguments against MVHR are pretty irrelevant tbh in the face of the sheer numbers on here who have it, like it and see the benefits. 

Since when did the number of posts otherwise make my case incorrect?. And please explain why it is irrelevant. This is serious.  Nobody has presented counter calculations or measurements and  no one has challenged my postings regarding energy efficiency with evidence to support their counter claims.  If you wish to post then please inform with facts.

 

I simply said that your assertion that MVHR is a luxury is wrong. 

 

I can only assume that by keeping on about it, in the face of people telling you how it works for them, how it's often secondary to the cost for them (because of the unarguable benefits) that you're a bit special in some way.

 

"Since when did the number of posts otherwise make my case incorrect?"

 

When did I say that? Don't quote me out of context or put words in my mouth please. 

 

[Redoctober]

I'm a bit late to this thread but I just want to say how interesting it is and to thank @DavidHughes for his view / findings on an MVHR system. 

I know a lot of members on here are converts and I can understand why that would be but for those members who are debating whether or not to install one, the arguments being out forward by David are valid..After all, it is my understanding that he isn't questioning the benefits of such a sysyem, he is just pointing out that they may not represent good value etc. 

As I have previously stated, I haven't installed one because on balance i could / didn't believe it represented good value and I took my lead from a well established House building Company who also shared the same view.

Therefore we should thank David for putting such an argument forward to allow others to become more informed etc??

[Onoff]

1 minute ago, Redoctober said:

good value

 

When looked at from a purely monetary point of view.

[Thedreamer]

2 minutes ago, Onoff said:

 

When looked at from a purely monetary point of view.

 

For your elderly relatives would a MEV (and trickle vents) be more suitable? I'm basing this on the assumptions that they don't live in a particular airtight home and the requirement is more for good ventilation rather than heat /cost efficiency?

[DavidHughes]

>Good draft sealing doesn't come even vaguely close to the sort of measures needed to get down to the sort of airtightness where MVHR starts to save worthwhile amounts of heat. 

Jeremy, please explain. a) why? b) even if you are correct, which I dont think you are, my heat loss calculations (which agree with yours) based on 100% sealed still present a conclusion that shows low benefit in terms of energy saved per year vs large initial outlay. I thought that this had already been tacitly agreed because nobody has come up with a counter argument. The house sealing issue has been gone over on many previous posts and just doesn't stand up to scrutiny in terms 9h heat lose.

[Onoff]

10 minutes ago, Thedreamer said:

 

For your elderly relatives would a MEV (and trickle vents) be more suitable? I'm basing this on the assumptions that they don't live in a particular airtight home and the requirement is more for good ventilation rather than heat /cost efficiency?

 

As in positive ventilation? I had considered that but tbh the upheaval might be too much for them at their age. I can't see it being long before we're talking care homes. Dad is so tight for instance he refused my offer to rewire the place some years back (would have cost him virtually nothing). Of late we've been trying to convince him to have the bathroom remodelled to assist the carers but he won't hear of it. Any talk of work in the house and just gets defensive and irrational (He's loaded btw ?).

[coconutsaregood]

On 21/03/2020 at 20:26, DavidHughes said:

>coconutsaregood

 

The air flow rates are set out in Building regulations Section F available online with a simple search.

 

To enable you to cut to the chase without reading and understanding 20 pages it requires an overall house ventilation rate of 0.3 x the area in square meters of your house in Litres/s. So 100m^2 house requires 30 L/s to comply with regs. There is no consideration of ceiling height or house volume the regulations probably assume around a 2.4m ceiling height in every room. There are specific requirements for extractor fans in bathrooms and kitchens to clear vapour on a maximum boost rate but unless you have an unusual house arrangement the two rules are largely the same give or take a few L/s.

 

If you want your house to be sellable then you must comply with this AND engage Building Regulations at the Council. If you don't need to do this then just DIY anything you like and live with it. In my last house I found 0.05-0.1 ACH perfectly acceptable but back then I wasn't subject to building regulations.

 

The DIY option works well as I did 20 years ago, but now the authorities want it tested and inspected.

 

David

 

 

 

 

 

sorry, got you now: 92 x 0.3 = 27.6 

ta

Edited March 23, 2020 by coconutsaregood
deduced the answer I was seeking.

[TerryE]

@DavidHughes, you seem to be adopting a very robust "prove my figures wrong or I'll ignore you" based on a set of predictive calcs.  I did my calcs 3-4 years ago and came to different conclusion: MVHR would save money and materially reduces running costs.  After almost 2½ years of live data and analysis of running costs, our actual energy bills and house performance closely tramline those pre-build calcs.  I can't recall the exact numbers but IIRC our system cost less than £3K to install and the heat recovery tipped us into the domain where we didn't need any space heating on our 1st or 2nd floors, so saved us a shed load of CH costs. 

 

We keep our entire house at 22-23°C 24×7 and our total annual energy bill is about 60% of our rates -- and that is with electric element heaters and not ASHP heating.  Our as-built experience is that MVHR saves money and materially reduces running costs.  Everyone that visits or stays at our house notices how fresh it feels / smells.

[DavidHughes]

>onoff

>All the facts, figures, calcs and arguments against MVHR are pretty irrelevant tbh in the face of the sheer numbers on here who have it

I am not quoting you out of context. I am quoting you very clearly in context. If you think that my comment on the number of counter posts with no substantiation is in anyway unfair then I wholly disagree and ask you to provide facts rather than conjecture. This is a discussion about whether mvhr is worth the price.

 

If you or any other contributors disagree with my assessment then please post with facts. The air quality issues have already been dealt with and so have the damp issues. For reference my view is that if there is a damp problem then it is probably best to address that first before considering an mvhr system.

[DavidHughes]

TerryE,

 

Quite the contrary, if I wished to ignore people I would not still be here. Please make your case and provide numbers to back up your summary. No one else has. This is my point. If you say it, please prove it with measurements and/or calculations. Anything else is just an opinion and with thousands of pounds at stake for the homeowner I think future non contributing readers will be very interested in the numbers.

 

 

[Onoff]

26 minutes ago, DavidHughes said:

>onoff

>All the facts, figures, calcs and arguments against MVHR are pretty irrelevant tbh in the face of the sheer numbers on here who have it

I am not quoting you out of context. I am quoting you very clearly in context. If you think that my comment on the number of counter posts with no substantiation is in anyway unfair then I wholly disagree and ask you to provide facts rather than conjecture. This is a discussion about whether mvhr is worth the price.

 

If you or any other contributors disagree with my assessment then please post with facts. The air quality issues have already been dealt with and so have the damp issues. For reference my view is that if there is a damp problem then it is probably best to address that first before considering an mvhr system.

 

WTF is wrong with you? Where did I mention damp? There you go again chucking in a statement ref damp and attributing it to something I said. 

 

I mentioned mould not damp. My inference was that it's down to a lack of the good, clean air flow/ constant air changes you get with MVHR. The presence of dust lends itself for mould spores to lodge and grow. You twist comments in an attempt to get your point across. Second time you've done it to my posts here.

 

In the face of that why bat on about cost?

 

You are just a very tenacious individual who has to have the last word. 

 

Are you on the spectrum may I ask?

[Onoff]

On the back of this somewhat fractious thread:

 

My understanding with what's happening ref Covid-19, is that if you are required to self isolate in an otherwise healthy household you should confine yourself to one room.

 

Would it be feasible to up the airflow from that one room to prevent spread of the virus to the rest of the house?

 

 

[Jeremy Harris]

14 hours ago, DavidHughes said:

 

Jeremy, please explain. a) why? b) even if you are correct, which I dont think you are, my heat loss calculations (which agree with yours) based on 100% sealed still present a conclusion that shows low benefit in terms of energy saved per year vs large initial outlay. I thought that this had already been tacitly agreed because nobody has come up with a counter argument. The house sealing issue has been gone over on many previous posts and just doesn't stand up to scrutiny in terms 9h heat lose.

 

Any chance you can use the quote function, please, so that we both get notifications properly and to make reading and replying a great deal easier?

 

The simple reason is that much of the air permeability will be through fabric that you cannot easily draft proof.  Masonry is inherently quite leaky, for example, as are other elements of the structure.  A chat with any builder who is building new houses will quickly show that, even to meet the pretty low demands of building regs, they have to radically change their approach to making the house less permeable by design.  Our house, like all new houses now, has an airtight/vapour tight barrier layer over the inside surface of the external structure of the whole house.  This is taped and sealed everywhere, including taped seals that connect this internal layer to the door and window frames.  It's really difficult, short of completely stripping an existing house back to a shell, to get close to this when trying to improve an existing house.

 

I think you've made your point clearly that for your particular circumstances, with an expensive installation in an existing house, where ventilation heat loss may not be the most significant heat loss element, you do not feel that MVHR is worth installing.  That's fine, but many others hold views, based on their experience, which are markedly different to yours, and those views are every bit as valid as your own.  The title of this thread is bogus, too, as it is clearly intended to be highly provocative and to create a firestorm of outrage.  You knew that when you chose it and that doesn't really endear people to respond calmly, IMHO.

 

My personal view is that the air quality alone in our house is something I would gladly pay a premium for.  Not having hay fever symptoms, because the pollen and spores are filtered out of the incoming fresh air alone makes it worth having.  The complete absence of condensation anywhere in the house, the rapid drying rate of towels and any washing we hang indoors, and the fact that we no longer use the tumble dryer are all additional reasons for having good ventilation.  I've never lived in a house with such good air quality in my entire life, and frankly I couldn't go back to living in a house without an effective form of continuous background ventilation. 

 

 

[ToughButterCup]

7 hours ago, Onoff said:

...

You are just a very tenacious individual who has to have the last word. 

...

 

If that's the case, then silence is the most powerful response. 

[Onoff]

4 minutes ago, AnonymousBosch said:

 

If that's the case, then silence is the most powerful response. 

 

Dog with a bone me...there's a word for it... ?

[Gone West]

@DavidHughes Well this is an interesting discussion. I haven't read the whole thread but from your original post I gather yours is a retrofit system in a bungalow without knowing the airtightness before fitting. I can't see any reason to doubt your calculations and in your position I wouldn't bother fitting a MVHR system either. I would be surprised if the same costs arose in a very low energy new build. For instance my new build is very airtight and is mainly heated by the electric towel rails in the bathrooms which means I have not had to install a main central heating system as the MVHR moves air around the house and maintains a pleasant 23C. I have not carried out any calculations to confirm this but I am very happy with the air quality and my electricity bills.

[nod]

Also late on the post

 

We didn’t add MVHR Main reason being a family friend that lives locally and self built 6 years ago advised us against installing 

Telling us while his system works well it drags in the smoke and smells from his neighbours stove and outdoor fires 

and suggested the same might happen with us 

It’s very difficult to get an objective opinion from someone who has already spent there hard earned cash on MVHR 

 

I installed two sets of bifolds 

Look great Probably hardly ever be used 

another side of the coin would be 

The money spent would have paid for MVHR 

Tricky one 

[Thedreamer]

21 minutes ago, nod said:

Also late on the post

 

We didn’t add MVHR Main reason being a family friend that lives locally and self built 6 years ago advised us against installing 

Telling us while his system works well it drags in the smoke and smells from his neighbours stove and outdoor fires 

and suggested the same might happen with us 

It’s very difficult to get an objective opinion from someone who has already spent there hard earned cash on MVHR 

 

I installed two sets of bifolds 

Look great Probably hardly ever be used 

another side of the coin would be 

The money spent would have paid for MVHR 

Tricky one 

 

During my commute to work I pass a church that has been renovated with MVHR fitted, the next property along is being gutted and currently has static caravan with a log burner. The amount of smoke that thing produces and is being sucked into the MVHR. This caravan has been there for years so this isn't a short term issue. 

 

At the end of day who cares if you fit MVHR or not it, your choice, your money.

 

 

 

[nod]

1 hour ago, Thedreamer said:

 

During my commute to work I pass a church that has been renovated with MVHR fitted, the next property along is being gutted and currently has static caravan with a log burner. The amount of smoke that thing produces and is being sucked into the MVHR. This caravan has been there for years so this isn't a short term issue. 

 

At the end of day who cares if you fit MVHR or not it, your choice, your money.

 

 

 

It wasn’t just the log burner 

His neighbour seems to have a fire going in the garden on a permanent basis 

We are near a main road he suggested that the same would happen with traffic fumes 

Enough to put my wife off

 

We have built a large house with UFH Well insulated and is cheap to keep at 18c 

Weve never used the upstairs heating 

So I’m not sure if we would have benefited from MVHR

It May have been just something else to go wrong 

 

We where required to put solar panels on the roof We ignited this as we don’t like the look of them and couldn’t see any way we would recoup the cost 

It’s all down to personal choice 

and budget 

 

[joe90]

5 hours ago, AnonymousBosch said:

 

If that's the case, then silence is the most powerful response. 

hence the reason I gave up with this thread.!

[Simplysimon]

don't suppose davidhughes is the real name of an architect that once posted here ?

[SteamyTea]

3 minutes ago, Simplysimon said:

don't suppose davidhughes is the real name of an architect that once posted here

Think his name was Martin.

 

[coconutsaregood]

On 21/03/2020 at 20:26, DavidHughes said:

>coconutsaregood

 

The air flow rates are set out in Building regulations Section F available online with a simple search.

 

To enable you to cut to the chase without reading and understanding 20 pages it requires an overall house ventilation rate of 0.3 x the area in square meters of your house in Litres/s. So 100m^2 house requires 30 L/s to comply with regs. There is no consideration of ceiling height or house volume the regulations probably assume around a 2.4m ceiling height in every room. There are specific requirements for extractor fans in bathrooms and kitchens to clear vapour on a maximum boost rate but unless you have an unusual house arrangement the two rules are largely the same give or take a few L/s.

 

If you want your house to be sellable then you must comply with this AND engage Building Regulations at the Council. If you don't need to do this then just DIY anything you like and live with it. In my last house I found 0.05-0.1 ACH perfectly acceptable but back then I wasn't subject to building regulations.

 

The DIY option works well as I did 20 years ago, but now the authorities want it tested and inspected.

 

David

 

 

 

 

 

Hello David, thanks for the reply and I am sorry I kind of ignored your response initially because I simply wanted the sum. I'm a little rusty on bldg regs these days and need to catch up, I still think in 1980s standards. The only constructive criticism I would add to your statement above is that "sick building syndrome" was a big topic in the past and the experts (CIBSE) state typical ventilation rates, for a dwelling, of one whole air change per hour to ensure the pollutants (including the ones less easy to sense and detect including perhaps: COVID 19) are diluted. 

 

So seeing fresh air rates, on this enthusiastic forum, of less than one I do find alarming. Yes you can live with it, but are they healthy? Building Regulations' minimum of around 0.43 air changes per hour, demonstrates the thinking has changed in recent decades but that is average. As we know you still need intermittent blast of fresh air for kitchens & utility rooms from a health requirement and WCs from the "wife" demands. These intermittent demand raise the average minimum.

 

Your argument with the guys on here will go on I see, as you try to overturn the converts with what we in the industry call Life Cycle Costs of the different solutions to air control in buildings. One aspect I can add is that Green buildings are seldom a good investment in terms of investment appraisal, so the selling point of Green tends to be the benefits that are subjective or emotional. I have the opinion that unless fossil fuels incur carbon tariffs (methane is way too cheap and competitive) Green will always struggle in investment terms and will continue until we run out of gas/oil and for now it will be up to wonderful Greta & others to persuade us all to change. The main point is you cannot take one function of a building in isolation, you have add it all together and look at the whole answer in terms of costs over the life or the term you are going to need the building. The value (the later is what you are all arguing about) of these things will increase as more people get educated or informed but the infamous estate agent is a barrier to progress on that front.  

 

thanks for reading and forget the cost argument it never works.

 

Edited March 24, 2020 by coconutsaregood
typos

[Mike]

12 hours ago, coconutsaregood said:

So seeing fresh air rates, on this enthusiastic forum, of less than one I do find alarming. Yes you can live with it, but are they healthy? Building Regulations' minimum of around 0.43 air changes per hour, demonstrates the thinking has changed in recent decades but that is average.

There have been various studies looking at this, mostly with positive results (no I've not read them all in detail), for example:

 

Snijders et al (2001) : Dedicated ventilation Systems may slow down the development of Chronic Obstructive Pulmonary Disease
Harving et al (1994) : Allergen-producing dust mites and fungi in is significantly lower
Feist et al (2001 & 2005): PassivHaus occupants report high levels of satisfaction (Note: Feist developed the PassivHaus standard)
Brunsgard and Jensen (2008 & 2009) : Ditto
Bretzke (2010) : Ditto for schools

 

There is also the possibility of including additional filters to reduce levels of pollution - NoX, for example - compared to outside air.

 

Pollution generated from the fabric, fittings and furnishings is a key topic, though. If you choose products that off-gas lots of VOCs, for example, then you're going to have an air quality problem irrespective of the nature of the ventilation system.

[coconutsaregood]

14 hours ago, Mike said:

Pollution generated from the fabric, fittings and furnishings is a key topic, though. If you choose products that off-gas lots of VOCs, for example, then you're going to have an air quality problem irrespective of the nature of the ventilation system.

 

Thanks Mike for the research on this matter. The current crisis should  afford me time to browse those papers. 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. Car exhaust fumes (filter required for intake air) is not a requirement for bldg regs but NO² generated inside is one (gas or  wood fumes).

Edited March 24, 2020 by coconutsaregood
NO² mentioned.