20 Nov 2009

Decide in haste — repent at leisure

Blimey. I am ever so slightly flabbergasted by the response to my last blog post on mechanical ventilation with heat recovery. I thought it was rather obscure and just a little boring, but thus far I’ve had ten responses and just about everybody disagrees with me. And what’s more, they all seem so anguished. Can it be that this is actually a very critical topic, and that what we are confronting here is a crucial issue? And why do commentators feel so threatened when I question the Passivhaus orthodoxy?

All I am saying is that I am not yet satisfied that the airtight/MVHR build route is the “way to go” for all new homes. I’m not set against it; I’d just like it to be tested in lots of real life UK situations before we embark on it as mandatory. I don’t think it’s that time critical. A delay of three or four years is nothing compared to making a horrible mistake. If this was a drug trial, we would be spending five years and billions of pounds putting it through its paces: why should we accept any less from a critical element of our future wellbeing and future build costs?

As the last respondent put it:

We cannot afford further delays.

I think we can. I don’t think the ice caps will melt any faster if we stand back and assess for a little while, rather than charging in.


  1. "I think we can. I don’t think the ice caps will melt any faster if we stand back and assess for a little while, rather than charging in. "

    Oh no no no.

    The 'message' at the moment is that there's some kind of important tipping point coming up within the next few months, and if we dont sign a big treaty by then it'll be too late.

    No, it doesnt make any sense to me either, but please... stay on message :)

  2. For me the anguish is for your credibility. I've had a lot of respect for your efforts but in this case it's quite apparent that you haven't done your homework but still continue to try to justify your opinion.

    It's also clear that the people entrusted with coming up with UK policy in this area haven't done their research properly either. There's a deep mistrust of the whole process, which is why I and others are upset.

    You say you want a trial "in the UK". I say please read the work that's already been done in Europe/Scandinavia, Canada and even some in the UK. Then come back with specific questions that you feel have not been already answered. Unless you feel that Brits are somehow fundamentally different to other people?

  3. "Unless you feel that Brits are somehow fundamentally different to other people?"

    No, but our climate is. Just because MVHR works in Sweden, doesn't mean it will work in the UK, because we "drive" our homes differently.

  4. I think some of the issue here and with many UK polcies on energy efficient housing is that people worry about the 'british' public.

    I know a lot of brits mentality toward housing is far different from most of the people that participate in energy efficient building design.

    BUT those that know and care will be able to deal with the POSSIBLE downfalls of MVHR, e.g. maintainance and making sure it is actaully working, and the ones that don't will have to learn bloody quick.

    I personally wouldn't conceve building an energy efficient house with an air permiability to match without mvhr.

    I, as many others, would build the most thermally insulative and airtight build possible/practical.

    With very airtight buildings, RHs could vary very rapidly. In my current house, which is not very air tight at all, RH can fulctuate uncomfortably in winter with the activity of cooking and showering and bathing etc.

    In a very air tight house, having the mvhr ticking over in the background will help reduce these sorts of fluctuations and help to recover this heat.

    I know that your arguement is that we have a mild climate in the UK and as such might not need the HR bit of the MVHR or indeed the MV bit, but I think that any benefit that is obtained in other countries is equally valid in the UK

  5. "I think some of the issue here and with many UK polcies on energy efficient housing is that people worry about the 'british' public."...........

    "BUT those that know and care will be able to deal with the POSSIBLE downfalls of MVHR,........" and presumably those that don't 'know and care' can get knotted.

    The thing that really disturbs me about the current approach to energy efficiency is that it is so authoritarian and so political. Even mention of open research or discussion seems to be percieved as a threat to the project. This is what we expect from politicians, not intelligent people, Politicians love top down decisions because it enhances their power and makes it look as if they know what is needed and are 'doing something'. It leads to nonsense like the 'banning' of incandescent lightbulbs - easy, superficial and at best a drop in the ocean.

    The truth is that the problem is an extremely complex one and the chances are that no one body, let alone the government, is going to get it all right first time. It seems bizarre to design houses without any input from the people that are going to live in them, this is how we got all those tower blocks in the 60's. Even if you don't give a stuff about democracy it would still be wise to consult and study ordiary people in the interests of education and getting compliance. They are not the enemy, you know.

  6. “Why do commentators feel so threatened?”:

    Threatened? No.
    Frustrated? Yes!

    Many of us know you as one of the most practical and level-headed people in the UK domestic construction sector, with a long-standing interest in energy efficiency, and you are seen as somebody who interprets and SOLVES problems.

    It is all the more surprising, therefore, to see you still worrying about MVHR’s, contrary to all the experience elsewhere, and the comments to your previous (but related) thread of 16.11.2009, which now includes the clear responses from Nick Grant and Wolfgang Feist.

    As far as timing is concerned, the Passivhaus offers such large energy savings that - however you want to debate the numbers - the sooner it is given a positive lead by those in positions of authority, the sooner the benefits will be gained.

  7. "Unless you feel that Brits are somehow fundamentally different to other people?"

    No, but our climate is. Just because MVHR works in Sweden, doesn't mean it will work in the UK, because we "drive" our homes differently.

    That's a pretty vague claim. How exactly would MVHR fail to work just in the UK?

    The HR bit is irrelevant to this debate. It's a technique for reducing energy demand but doesn't affect the users' experience. What you're claiming is that mechanical ventilation might not work. It works in homes now and I haven't heard of major problems. It works in many, many offices.

    So please point to any specific problems if you know of any!

  8. “Why do commentators feel so threatened?”:

    Threatened? No.
    Frustrated? Yes!

    My feelings exactly, Anonymous

    Are there points for guessing identity of anonymous posters??

  9. I can see buildingstoat’s point that persuasion is better than coercion. Indeed I wish our government had thought likewise, and had provided the substantial ‘carrots’ that have been available for the PassivHaus on the continent for many years.

    Well, it hasn’t, and it also declined the opportunity to take part in just the sort of local demonstration trial you envisage (eg the CEPHEUS programme, several years ago). Fortunately, though the UK missed that opportunity, we have nevertheless gained from the results of the work (and from many other sources) and now have all the reliable calculation tools we need for UK passive houses.

    Meanwhile, without a government definition of ‘zero carbon’, confusion and contradiction reign supreme. The result: articles such as the recent (Daily Telegraph, 13.11.09) report on “eco pioneers” who have been landed with a system that requires electric underfloor heating when the difference between inside and outside is 10 degrees. Energy efficient?

    With the PassivHaus standard I know exactly where I am, know that the balance between construction costs and running costs is favourable, and know that energy consumption will be very low indeed.

    As a scientist, the research and trials already undertaken in various climates are, to my mind, exhaustive and convincing evidence for the suitability of passive houses for Britain.

  10. I spent C$3000 for a high-efficiency (Lifebreath 195DCS) HRV including installation & ductwork. The lowest quote I had was ~$2500 for base model. $500 would have got me decent exhaust fans for the bathrooms and then I could have spent the $2000-$2500 for triple-glazed windows instead of double.

    If someone can explain how I didn't make the stupid choice, at least it might make me feel a bit better. ;-)

  11. The underlying problem in in Britain seems to me that Britain has an extremely low fraction of self-built homes (for reasons that I haven't quite understood yet). For the overwhelming majority of houses built in Britain, the buyers of the houses had no influence on their design, and therefore had no reason to inform themselves about what interesting now technologies are available.

    This leads to an unusually conservative market for building technologies, which are taken up in Britain far slower than in regions with a higher rate of self-built homes. Demand is driven here by building regulations rather than by home-owner preferences.

    There are simpler and more stimulating ways for the government to encourage the large-scale trial of low-energy technologies:

    - encourage self-build projects by having local councils make individual serviced plots available, rather than only entire large fields that only commercial developers can exploit;

    - provide tax breaks for mortgages on houses that fulfill energy-efficiency standards (like the KfW-Haus in Germany)

    If you want a more innovative residential building-technology industry, you need more self-builders.

  12. I very much agree Marcus, but is it innovation they want?

    The way things have been going in the last few years, the goal seems to be to go for ever greater standardisation. More and more Regulations come from the top down and get ever more prescriptive. From Berwick to Bude and Dover to Derby everyone MUST do x,y and z, despite differnt climates, uses or site locations and certainly irresective of the wishes of the occupants. Just look at the way Part M has been handled.

    The earlier building regulations were clear and specific and concentrated solely on what had to be done. The newer ones (e.g. Part L, Part P) specify WHO has to do the work - difficult for self builders but no problem for the big boys.

    No, self-builders are something that this government neither likes nor understands

  13. To the question of is MVHR worthwhile in the mild, damp UK climate; I can't offer experience of MVHR yet but I can offer experience that seems to suggest it would be useful.

    We recently externally insulated our 19th cent stone house, replaced doors and windows, and made it very airtight. (One of whatever unit it is you measure airtightness in). However MVHR still awaiting installation. Once the weather started to cool in October, we became very excited about how warm the house remained, how the heat from day to day activities was being conserved in the house and keeping us warm without any extra heating.

    Then the mould started to grow, and the salt stopped coming out of the salt shaker. Those activities (showering, using the dishwasher, cooking) that produced all that handy heat, also produced lots of annoying water wapour. So we had to fling open the windows once again, and fire up the heating. Now we are basically burning gas just to keep dry. Correct me if I'm wrong, but my understanding of MVHR is that I get to lose the moisture but keep the heat.

    I can't help suspecting that the 40-odd watts of the MVHR fan might do this more efficiently, and at least as effectively, as opening the windows and turning on the heating. Others have done the sums on this, and I believe they think it does.

    I also recognise that there is a lot of scepticism in the UK about MVHR still. So I think when we do get ours fitted, we should probably make a few notes and measurements to share.

    As for the typical UK resident not understanding how to use MVHR, and therefore wasting energy – well isn't 40W a lot less to waste than some common British vices, especially as a lot of people will get the hang of a Passiv-style house, and not open windows when they don't need to etc, but instead enjoy the benefits intelligently. (These might even be occupants of the same house, 5 years later)

    And is the risk that some people will waste the MVHR benefits and fan energy some of the time, a worse risk than building "energy efficient" homes with high levels of insulation and airtightness, and relying on the occupants to ventilate them properly themselves. Judging from my experience, if we go down that road, a lot of people will be growing a lot of mould (and dust mites etc) and/or having to open the windows and let out precious heat, just so they can get some salt onto their chips.

  14. Kate,

    A very interesting story well told. It certainly seems you need to do something about your air quality and mechanical ventilation might well be it.

    However, I think one of the points Mark is making is that whereas in, say Canada, you can rely on the incoming air being very dry in winter because it is much colder, that might not be as so here. Today we had outside temperature of 13 deg C and so much rain the humidity must have been near 100%. The hall temperature was 18 C. - not such a big difference. It might just be that the best solution is a de-humidifier, about 200W, more than MHVR but a whole lot less than heating.

    I have experienced MHVR in the Alps and it was OK. not silent but I could live with it. My problem with this proposal is the REQUIREMENT that everyone MUST have it, like it or not, whatever the circumstances. I can't for the life of my see what's wrong with trying it out first, surely a much better way of getting it accepted if it proves useful.

  15. Beautifully told Kate

    Building Stoat

    Here I am sat at 20C and its under 12 outside and has stopped raining which has dropped the RH to 50% if my hygrometer is to be believed. Indoor RH says 45% and feels lovely. No MVHR so we are loosing heat but outdoor air and temp difference seems enough combined with some averaging out and the mysterious but sometimes overrated power of moisture buffering.

    Sure if it stayed at 100% humidity and 13C outside for a long time, indoor humidity would rise to about 60% plus moisture generated in the house but that doesn't seem to happen very often or for long (sadly I have a graph of half hourly RH, temp and dewpoint in front of me!).

    Back to the topic in hand I agree MVHR is no simple magic bullet but what is? If we don't mind loosing heat it is simple, vent plenty and top up the heat with boiler.

    However if we save energy then ventilation needs to be controlled in some way and also needs something to drive it when wind drops and temperatures even out. MEV does the trick and is simpler and cheaper than HRV but it leaves us with an energy loss that could be saved. Pay your money and make your choice.

    And yes people do tape over trickle vents, switch off fans and all the rest so if anyone can come up with something fool proof it should really take off.

    Whilst an advocate of PH and HRV I don't think either should be compulsory tomorrow but I agree with anonymous that we don't need to trial them either. We might need to learn from our mistakes and evolve both the technology and our culture as we have with pretty much everything around us.

    What I think should be compulsory for new build is good insulation, zero thermal bridging (based on external dimensions) and excellent airtightness. All these are nigh on impossible to retrofit later.

  16. I'm quite surprised about the fervor of the responses regarding passive house, it seems to be considered irresponsible to question it as an orthodoxy?

    We've recently completed a social housing project with MVHR, and Im fairly certain some people have turned theirs off (from the smell!). Its subject to monitoring, so we will find out soon enough, however I know from the performance results that people just cant be bothered to use the houses correctly, despite training, instruction manuals etc. I would worry about using PH in social housing, the consequences of turning it off seem fairly drastic, and lets face it we've all seen overflow pipes spilling water down facades for years with no one doing anything about it, and thats visible. Surely there is an alternative to PH?