K78

Health risks associated with passive houses

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2 minutes ago, tonyshouse said:

As you say interesting, I can't see the aerodynamic cooling effect ever coming into play it is a small effect.

 

I can see roof surfaces getting very cold due to radiative cooling and to a lesser extent by evaporative cooling ...

 

Interesting; it's purely gut instinct (I've not attempted any calculations), but I'd have thought the reverse - that radiative cooling is quite a small effect, aerodynamic much larger.

 

The kicker with aerodynamic cooling is that it's pretty much continuous, if you've got a prevailing wind: you're feeding a continuous supply of moisture-laden air across a condensing surface that is continually being cooled by the flow.

 

Evaporative cooling can be huge.

 

Since we're getting into all sorts of digressions: I'm an angler, and as a youth I used to drive all manner of silly sports cars (Caterham Seven type stuff). One of my tricks was to wrap my catch in a soaking towel and strap it to the rollover bar for the drive home. The evaporative cooling could mean that the fish was literally freezing to the touch, even when you 'd driven home on a warm August evening - quite remarkable, I always thought!

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32 minutes ago, Sensus said:

 

That's because you're forgetting Rule 2 of Plot Finding: most plots never reach the open market.

 

Rule 1, incidentally, is that any plot that does find its way to the open market is, by definition, grossly overpriced. ;)

 

 

Of the 6 plots we have bought over the years, 4 have been purchased privately, 2 on the open market.  Of those 2, I was able to negotiate the price down on one, but went to a closing date with the other.  TBH, it's not difficult to find a site privately, it's just a case of doing a bit of detective work, identifying potential sites, finding out who the owner is and approaching them.

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I think sensus has made some excellent points and is obviously very experienced in this matter. 

 

The points he makes around MVHR have always been a concern for me. I always wondered how they could adequately serve a house without multiple vents and a high flow rate. 

 

A quick google of "passive house problems" and "passive house health risks" brings up a lot. 

 

Summer over heating seems to be a big issue with many passive developments in the uk.  Apparently heat builds up faster than ventilation can remove it leading to 25C+ temperatures for days, even weeks at a time. 

 

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19 minutes ago, Stones said:

Are the problems  / potential problems that have been raised a good enough reason to halt progressive improvements to building standards? 

 

...Is there a particular body or group that you feel has unduly influenced policy making?

 

1) I would say yes. So, it seems, would a lot of the people actually responsible for formulating changes to the Building Regulations. As I've said further up the thread, there does actually seem to be a general acknowledgement amongst Building Control bodies that Parts C and F need a very substantial overhaul, underpinned by thorough research, before Part L can be taken much further.

 

2) Not necessarily, no.. for the simple reason that that policy making has not been unduly influenced, because it is not, as yet, accepting PassivHaus as the way forward within the Regulations.

 

Even the BRE, who effectively administer PassivHaus in the UK, do not promote it as such, and they are the single organisation, if any, best placed to make that judgement.

 

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50 minutes ago, Sensus said:

But we digress?

 

Not sure. You said that the small self-build market is not worth much attention. I just noted that the size is limited entirely artificially. When the farm next to us was bought and developed there was no such thing as offering public to buy plots, otherwise we would not have ended up with monstrosities at a ridiculous price.

http://www.getsurrey.co.uk/news/surrey-news/brookwood-farm-sale-nets-28m-7123244

http://www.rightmove.co.uk/developer/branch/CALA-Homes/Brookwood-Farm-97141.html

http://www.rightmove.co.uk/new-homes-for-sale/property-55574881.html

Note they never even show the land strip on these plans - so tiny they are. Now, split the 16 acres to say 100 proper homes (plus roads and a school) and you will get reasonable plots at around 300K max + the build itself, people would actually get something quite decent.

 

Incidentally, my personal view on the regs may be not far from yours but for a  completely different reason. I would rather regs controlled only safe vs unsafe leaving the rest to the market. Enough competition would sort it out reasonably quickly. I do agree it is annoying to build bad houses nowadays due to wasted resources though. If the proper stock was being built in the first place there would not have been so many improvement projects that start sometimes 3 years into the life in a new house.

 

Again, back to the point. You said developers are limited by the market. Can you quantify how much more expensive it is to create a warm attic as opposed to cold one at the time of original build? I would be surprised if it was more than 10K - that is for extra 20 to 40m2 of space + storage at eaves.

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3 hours ago, Sensus said:

 

If Google can find it for me, it can find it for you, too. I'm not your personal research assistant. :P

 

If you know anything about aerodynamics, you'll know that eddy currents need relatively high velocities before they become meaningful;

 

 

Like I said, I'd searched, but found any data to support your assertion elusive, so thought I'd give you the opportunity to post a reference. But if it doesn't exist, it can remain an 'intersting' theory.?

 

And my comments on eddy currents are informed by my knowledge of automotive aerodynamics and CFD analysis. Your statement may be correct in the context  of vehicle aero, but that's not the context of this discussion.

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8 minutes ago, oldkettle said:

 

1) Not sure....

 

2) Incidentally, my personal view on the regs may be not far from yours but for a  completely different reason. I would rather regs controlled only safe vs unsafe leaving the rest to the market. Enough competition would sort it out reasonably quickly. I do agree it is annoying to build bad houses nowadays due to wasted resources though. If the proper stock was being built in the first place there would not have been so many improvement projects that start sometimes 3 years into the life in a new house.

 

3) Again, back to the point. You said developers are limited by the market. Can you quantify how much more expensive it is to create a warm attic as opposed to cold one at the time of original build? I would be surprised if it was more than 10K - that is for extra 20 to 40m2 of space + storage at eaves.

 

1) This is a debate for another thread, I think.

 

But if plots were to be offered for sale on major developments (as they are in some instances), they would still be limited by the same planning criteria.  Look at the SCHLAA for any LPA and you will see that they assess the number of plots that can be delivered from any land allocation. We've now got rid of the hard-and-fast rule that existed under PPG3 that any residential development must demonstrate a density of at least 30dph, but the emphasis is still on the efficient use of land. You won't see any great change in the overall form of development, just because some of it is delivered by self-builders: self building doesn't create and more usable land, and the Planning imperative will still be on getting the most houses out of the little that's available.

 

What you will see, to put it bluntly, is a dramatic drop-off in the rate of construction of new houses. The reason that not many developments include plots for self-builders is that it's an exercise in herding cats.

 

I won't get into the financial and economic complexities of delivering infrastructure on large self build schemes, other than to say that 'challenging' is an understatement!

 

2) I actually agree with you entirely on your view that legislation should control only what is necessary to a basic level, leaving the rest to the market. To be fair, I think that the current Regs do a reasonable job of achieving this.

 

3) It varies according to design, of course, but the basic rule-of-thumb that I was given by out Surveyors in the last major housebuilder I worked for was that habitable roof space costs about 15% more per m2 of floor area, whilst on the other hand (because of the sloping ceiling areas: the RICs measure 'useable' floor space as anything with a height of 1500mm or more) our Sales team advised me that room-in-roof needed to be discounted by as much as 25% in terms of sales price per square metre.

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1 hour ago, Stones said:


 

Of the 6 plots we have bought over the years, 4 have been purchased privately, 2 on the open market.  Of those 2, I was able to negotiate the price down on one, but went to a closing date with the other.  TBH, it's not difficult to find a site privately, it's just a case of doing a bit of detective work, identifying potential sites, finding out who the owner is and approaching them.

That is true of Scotland, and indeed that is how I got the present house plot.

 

But where we were down south in Oxfordshire, I found several lovely looking potential plots, found the owner, only to be told it has tried and failed for planning before.  Even what look like obvious infill sites that would be pretty much guaranteed to get permission up here were "green belt" and not allowed, even if between two existing houses in a village.  That may have relaxed a bit now?  The one that stands out to me was a lovely little timber barn in between two houses in the village, refused permission to convert to a house several times.
 

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16 minutes ago, Sensus said:

3) It varies according to design, of course, but the basic rule-of-thumb that I was given by out Surveyors in the last major housebuilder I worked for was that habitable roof space costs about 15% more per m2 of floor area, whilst on the other hand (because of the sloping ceiling areas: the RICs measure 'useable' floor space as anything with a height of 1500mm or more) our Sales team advised me that room-in-roof needed to be discounted by as much as 25% in terms of sales price per square metre.

 

I would quite specifically want to get an idea not for building walls and creating a proper roof in the attic but just for making the space warm as opposed to cold. I can see from the quotes I have got for my extension so far that the difference for our roughly 90m2 of footprint is quite small, 15K at most - and this is against Warmcell roof. And if we take £1000 as a rough guide cost for developers then 15% extra makes it £150*40m2=6K. Would you say this number makes sense? If it does, would you say enough people would be willing to pay 6K for this extra space?

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2 minutes ago, ProDave said:

But where we were down south in Oxfordshire, I found several lovely looking potential plots, found the owner, only to be told it has tried and failed for planning before.  Even what look like obvious infill sites that would be pretty much guaranteed to get permission up here were "green belt" and not allowed, even if between two existing houses in a village.  That may have relaxed a bit now?  The one that stands out to me was a lovely little timber barn in between two houses in the village, refused permission to convert to a house several times.

 

If it's a plot in a village, the issue is more likely to be one of the sustainability of the settlement, rather than 'green belt' location, per se, and yes, that's a fairly common problem (with some standard, albeit not universally applicable, solutions).

 

There are now Permitted Development rights for the conversion of redundant agricultural buildings to dwellings in England, of course, with their own reasonably clear and detailed rules.

 

But again, such problems can be largely bypassed if you have sufficient expertise in the Planning system. It's why companies like mine can offer plot search services and it be good value for money... we'd have started with an analysis of the Local Plan, to determine which settlements in the LPA are considered to be sustainable and therefore suitable for further infill development. Much of the work can be done simply and quickly by desktop study.

 

The plots are there - really they are - it's just that you need to know how to go about looking for them effectively and be committed enough to put the effort in.

 

The new legislation is intended to remove the obstacle of needing this Planning expertise, because in theory the Planning department will be doing the hard work for you. In practice, it falls foul of Rule Nos. 1 and 2, but the Politicians aren't sophisticated enough to have realised that and (as usual) look likely to fall foul of the Laws of Untended Consequences.

 

12 minutes ago, oldkettle said:

And if we take £1000 as a rough guide cost for developers then 15% extra makes it £150*40m2=6K. Would you say this number makes sense? If it does, would you say enough people would be willing to pay 6K for this extra space?

 

No, it's 15% on top of the normal cost of the floor area, so if you're suggesting £1,000/m2 for 'normal' floor area, then it would be £1,150/m2 for half storey, room-in-roof construction. Though if I suggested to any major developer that they should be spending £1,000/m2 on building their houses, I'd be likely to get hot coffee sprayed in my face. :)

 

And if the estate agents had given us a figure of, say £2,000/m2 for sales prices on 'normal' floor area, then we'd be discounting the value of the floor area for the half storey, room-in-roof down to anything as low as £1,500/m2
 

I should stress that these figures are for half-storey room-in-roof, as most developer housing doesn't have a large enough footprint for a true 'attic' storey to be worthwhile.

 

I don't want to derail this thread any more than we have already, but if you want to start a new thread on the economics of room-in-roof construction, then I'll be happy to contribute further, if and when I can find the time.

 

Ditto plotfinding. :)

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5 hours ago, Sensus said:

 

That's certainly what they say. :)

 

We offer a plot finding service. I recently did a report for a client against very specific requirements (plot of a certain size, suitable for a wheelchair accessible bungalow, within the existing settlement boundary of a specific and quite small market town, for family reasons). We came up with a shortlist (there were several more lesser prospects) of 15 viable options within a few days.

 

I'm rather inclined to think, therefore, that it's more a case of self-builders either:

  • lacking the expertise to identify and pursue suitable plots
  • being too choosy or;
  • lacking the finance to pursue the genuine opportunities.

The recent changes to Planning may help, as they put an onus on the 'professionals' to spoon-feed self-builders with a supply of plots, but I doubt we'll see any sort of wholesale transformation of the market.

 

For what it's worth, the major housebuilders are primarily limited by land supply, too: don't be deceived into thinking that it's a problem limited exclusively to self-builders.

 

But we digress?

 

It is also where the plots are, and I think that the current self-build community is very fussy and perhaps still looking to make a profit as well as a home in some cases.

 

I can point you to plots starting at about 35k, all within an hour of Sheffield, Derby and Nottingham, or half an hour followed by 1:45 hours to London on the train.

 

Mansfield District Council is struggling to sell land in good areas with Outline PP for £200k an acre. The train journey to the regional centre - Nottingham - is under half an hour with trains from about 6am to late evening.

 

As if by magic, here is a small 258sqm plot in a cul de sac near here which has just sold for £35k (advertised at £45k) after several months. Probably suitable for a compact 3 bed detached or 2 bed bungalow. I think I could have a 1000sqft 2 bed nearly passive bungalow built on that for around £100k plus the plot - but little or no profit in it as a sale.

http://www.rightmove.co.uk/property-for-sale/property-37649083.html

 

Original ad:

http://www.zoopla.co.uk/for-sale/details/41781573?search_identifier=c7db1d80e8e63c0757967fedfbf15181#4kv4Apdvw6t72aTw.97

 

For a comparator this 3 bed 2 recep garage house on a larger plot 3 or 4 doors down is on at £160k

http://www.zoopla.co.uk/for-sale/details/41175270?search_identifier=c7db1d80e8e63c0757967fedfbf15181#BbmgvCMUcH5kcYj3.97

 

Ferdinand

 

Edited by Ferdinand
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3 hours ago, K78 said:

I think sensus has made some excellent points and is obviously very experienced in this matter. 

 

The points he makes around MVHR have always been a concern for me. I always wondered how they could adequately serve a house without multiple vents and a high flow rate. 

 

A quick google of "passive house problems" and "passive house health risks" brings up a lot. 

 

Summer over heating seems to be a big issue with many passive developments in the uk.  Apparently heat builds up faster than ventilation can remove it leading to 25C+ temperatures for days, even weeks at a time. 

 

 

I just had a quick scan through the Page 1 results searching 'passive house health risks'.  Two things stood out, the first was the use of earth pipes to preheat incoming air for MVHR, and yes absolutely, there are  documented problems with that particular 'technology'. From what I remember from previously discussing this, to make it work you needed very expensive pipe which had some sort of (silver?) lining to kill of the harmful bacteria that could accumulate in the pipe. I do remember a rep at one of the building shows giving me a ballpark figure for the pipe, and me falling about laughing until he said he was deadly serious.

 

The second thing that stood out was the many references to insufficient ventilation, caused by either poor design (incorrect ACH specified) or end user mismanagement (not servicing filters, closing vents, reducing airflow to reduce noise).  To me the answer to many of these supposed health risks would be to increase the rate of ventilation (ACH).  I really can't get my head around why this is such an issue.  Noise I can perhaps accept, if a unit was constantly on a boost / its highest setting, but that to me at any rate would indicate an undersized or incorrectly specified MVHR unit.  Otherwise, what's wrong with increasing the rate of ventilation?  Okay, you maybe then do not fall within the passive house parameters because you have marginally exceeded the threshold heating requirement, but so what?

 

It strikes me that the thing that really needs to change in terms of building regs are the ventilation rates.  Do they take into account the realities of modern day living - drying large amounts of laundry inside, lots of showers etc?  Both of these things are relatively recent additions to the way we live and probably some of the biggest contributors to the amount of moisture in a house.  Skip back 30 years and showers were starting to make serious inroads into our ablutions, but prior to that we relied on baths, which may have been daily, but equally could have been weekly.  The amount of laundry we now generate is undoubtedly linked to the ease with which things can now be washed by machine.  Again skip back 30 years and twin tubs and washing days were still common.

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Re modern day living / lifestyles.

 

I used to be a buy to let landlord. One of our properties was a 1980's 1 bedroom flat. Timber framed (4") and double glazed.

 

It was "normal" for tenants to turn off the bathroom fan because of the noise, then complain about the mould in the bathroom. That's when I decided to ignore wiring regs and remove the fan isolator switch so it was not possible to disable the fan. Light is on, fan is on (then stays on with a timer) NOT negotiable and no facility to disable it.

 

Trickle vents on windows were NEVER open.

 

One tenant in particular complained of "water running down the walls"  On investigation, the heating was off so the flat was cold (were they happy to live like that) and every room had a clothes horse with dripping wet washing hung on it. They didn't seem to want to use the clothes line outside or the tumble dryer in the shed.

 

After that tenant left (god riddance) I never had a condensation problem again.

 

I guess it boils down to "poverty" they could neither afford to turn the heating on or use the tumble dryer, yet expected the landlord to magically solve the problem.

 

So the ideal social housing will have mvhr AND heating that you CANNOT turn off.
 

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1 hour ago, Stones said:

It strikes me that the thing that really needs to change in terms of building regs are the ventilation rates.  Do they take into account the realities of modern day living - drying large amounts of laundry inside, lots of showers etc?  Both of these things are relatively recent additions to the way we live and probably some of the biggest contributors to the amount of moisture in a house.  Skip back 30 years and showers were starting to make serious inroads into our ablutions, but prior to that we relied on baths, which may have been daily, but equally could have been weekly.  The amount of laundry we now generate is undoubtedly linked to the ease with which things can now be washed by machine.  Again skip back 30 years and twin tubs and washing days were still common.

 

I would quite like to explore the relationship between increased ventilation and increased heating cost. Relevant to passive but also relevant to the new environment created when old houses are double glazed and treated for draughts - even as crudely as door sealing etc.

 

My experence of older (pre-1950) houses is that insulating well plus double glazing and upvc doors with seals is still a very significant improvement even if there is still a lot of ventilation.

 

I can point to one where we only got as far as half double glazing, which had condensation issue with the remaining single glazed bays. That was fixed with trickle vents to those rooms with the "close the vent" shutters removed on fitting. But it was still a warm, relatively inexpensive house compared to others those Ts had lived in. It is due to become a road now.

 

Another we have reduced the energy bills by about 60-65% by insulate / double glaze / board out as convenient doing other work. The T has an indoors/outdoors lifestyle due to a statistically significant qty of dogs (8-10 depending). It also has a loft-fan fitted which was in before we double glazed etc; that may now be unnecessary.

 

Typically the statement seems to be that leakage account for perhaps 30% of lost heat. How much of that leakage do we actually need to keep, and is there a method to find out for a particular property other than by suck-it-and-see?

 

Can we fix a stuffy passive house by fitting a couple of HR trickle extractor fans, a leaky cat flap and a non-sealed loft hatch :-) ?

 

Ferdinand

Edited by Ferdinand
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On 7 October 2016 at 08:20, Barney12 said:

 

2. Remove or reduce all windows. I know you've bought a plot with a view but seriously saving on your energy bills is way more important than a view.

 

 

Couldn't disagree more. 

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23 minutes ago, worldwidewebs said:

 

Couldn't disagree more. 

Whoosh....

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20 hours ago, Sensus said:

 

That's because you're forgetting Rule 2 of Plot Finding: most plots never reach the open market.

 

Rule 1, incidentally, is that any plot that does find its way to the open market is, by definition, grossly overpriced. ;)

 

 

Is there a season for buying plots?

 

Rather like one season for buying houses being the next 3 months if you can find what you want :-).

 

Ferdinand

 

Edited by Ferdinand

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30 minutes ago, Ferdinand said:

 

Is there a season for buying plots?

 

Rather like one season for buying houses being the next 3 months if you can find what you want :-).

 

Ferdinand

 

Yeh it's called recession. Mate currently building out a site bought around 2010 for less than 10%gdv

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17 hours ago, Ferdinand said:

 

... I think that the current self-build community is very fussy and perhaps still looking to make a profit as well as a home in some cases.

 

 

That's where the latest Government legislation falls foul of Rule 1: you can bet your ass that any land that has been earmarked for self build will be (over)priced especially for self builders... which means allowing negligible profit margin.

 

Back on topic:

 

16 hours ago, Stones said:

To me the answer to many of these supposed health risks would be to increase the rate of ventilation (ACH).  I really can't get my head around why this is such an issue.  Noise I can perhaps accept, if a unit was constantly on a boost / its highest setting, but that to me at any rate would indicate an undersized or incorrectly specified MVHR unit.  Otherwise, what's wrong with increasing the rate of ventilation?  Okay, you maybe then do not fall within the passive house parameters because you have marginally exceeded the threshold heating requirement, but so what?

 

Ventilation is definitely one of the current weak spots, both with PH and the latest Regs (management of solar gain and thermal mass is the other).

 

The problem is that current MVHR is actually incredibly crude when you look at it - I'm absolutely positive that the systems we're using today will be treated with disdain in a couple of decades, and my worry is that the PassivHaus units that have been built with these systems as an integral part of their design will be looked upon in much the same way as we look at the Airey houses of the 40's and 50's.

 

Noise is one issue, but the other - more significant one - is that if you simply crank up a current MVHR system to the point where it delivers sufficient air change rates for health and wellbeing, you create uncomfortable drafts. I've got my own thoughts on how you might deliver an MVHR system that overcomes this, but I'll keep them to myself for the moment, as a Patent application may be appropriate in due course.

 

Humans are finicky devices, with very narrow (and individually variable) comfort zones, so the 'one size fits all' approach of PH is onto a loser from the start. They spend quite a lot of time teaching you about this stuff (environmental comfort zones) at University, if you do an Architecture degree. For anyone with a serious interest, I would recommend Spon's 'Ventilation of Buildings by Hazim Awbi' or 'Ventilation Systems: Design and Performance' by the same author.

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@Sensus

 

Yes there are perhaps some obvious alternatives to improve the distribution without adding much cost, perhaps applying the principle of the Leaky Hose to air, even controlled by WiFi if necessary, perhaps with holes getting larger away from the source. People on here could self-experiment with that using normal ducting and holes every 0.5 to 1m and some 'corks' i.e. Adjustable hit and miss vents.

 

Circs permitting it might be interesting to put all the services under grills round the room periphery as  in a Victorian church.

 

Best of luck.

 

I think the key thing is what we in software development call Maintainabilty, in this context the ability to change all the services without destroying the fabric. I try to do that in my small way when renovating.

 

On the books, I just spent £50 of my book budget on a study of houses built by Peter Aldington from the RIBA, which is superb. So SPONS will go begging for now.

https://www.amazon.co.uk/Houses-Created-Peter-Aldington/dp/1859467008

 

Ferdinand

 

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2 hours ago, Ferdinand said:


 

I think the key thing is what we in software development call Maintainabilty, in this context the ability to change all the services without destroying the fabric. I try to do that in my small way when renovating.



 

Going off topic here, but when I lay my upstairs flooring (chipboard and carpet) I will leave a strip of boards probably 300mm wide that are only screwed down around the perimeter of each room and can be lifted should I need to add e.g any extra wiring.  I did this in my previous house and it worked well. the only reason I did not do it in the present house was we have UFH upstairs.

 

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I have just been reading this thread in catching up.  Some interesting perspectives, and controversial opinions. Some general comments / responses.

  • The audience in this forum is a highly biased one: people interested in self-build development. Moreover,  those who want to take an interest in the informed opinion of peers.
  • From my personal research the main risks with MVHR relate to poor maintenance and ignorance of the occupiers. I don't think this is relevant to most visitors to this forum.
  • IMO,  the risks in modern well sealed houses are in those without correctly operated MVHR (and closed trickle vents, etc.).
  • @Sensus comments about the risks of condensation due to poor airflow and dead zones in MVHR-fitted houses, seem anecdotal rather than evidence based.  They have no underpinning in the physics of gas diffusion.  It just doesn't work that way.  Heat exchange drops the RH of input air at 0°C and RH 60% to something like 20% at 20°C. The walls in a house like mine are typically within 1°C of room temp.   Even the surfaces nearer cold bridges around the windows will only get down to say 15°C under the most extreme conditions.  Gas defusion and micro circulation means that the AH in the room will rarely vary a few %.   The only material condensation occurs in the MVHR unit itself,  and this is designed to discharge it safely.  Yes,  we will be adding to the moisture levels by inhabitation, but only to comfortable and safe levels. 
  • On a different point in some regions decent self-build plots are extremely difficult to come by.   We were lucky enough to a have a garden large enough to split, and survived the LPA cat and mouse game to get planning permission.  The other alternative here is to buy a rundown property,  demolish and rebuild.   The local LPA is really only interested in supporting large developments in designated development villages. 
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1 hour ago, TerryE said:
  • @Sensus ...Heat exchange drops the RH of input air at 0°C and RH 60% to something like 20% at 20°C. The walls in a house like mine are typically within 1°C of room temp.  .... Yes,  we will be adding to the moisture levels by inhabitation, but only to comfortable and safe levels. 

 

 

The big flaw in that thinking is that you are assuming that the moisture comes in with the air from the outside! The problem comes with the often massive (well in excess of 100% RH at room temperature) amounts of moisture that can be added by occupants.

 

I don't mind you criticising evidence that I have seen with my own eyes (and discussed with the experts at the BRE) as anecdotal, but to then conclude your critique with a wild (and entirely inaccurate) assumption of your own rather undermines your argument! :D

 

I would also reiterate what I've already pointed out in a previous post (though perhaps not sufficiently explicitly): you don't need to get condensation (100% RH at surface contact) to get mold growth. An AW of 0.6 is sufficient.

 

Also, whilst cosmetically unsightly, black mold is merely a potential indicator of of the real problem, not the problem itself: what we should be really worried about is the build-up of pathogens and contaminants that are detrimental to human health.

 

Edited by Sensus

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If anyone wants to do their own research and draw their own conclusions on some of this then you could do better than start here. ...

 

http://hope.epfl.ch/

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