K78

Health risks associated with passive houses

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4 minutes ago, gravelld said:

But that ain't evidence.

 

 

I agree completely.  

 

I treat PH certification as being something like very modern design.  It may well put off a lot of people, but it's just as likely to spark greater interest in at least some of those who aren't put off.  Whether that impacts the final price is probably very situation dependent. 

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1 hour ago, jack said:

I don't believe the word Passivhaus by itself is a trademark.  From memory they only have a trademark on the logo.  There may be a question over whether the word "Passivhaus" is confusingly similar to the logo.

 

 

Wolfgang Feist would appear to own a number of EU related marks for both "passivhaus" and "passive house".

Figurative marks with letters provide protection against the use of the words too. [insert blurb about the technicalities of trade mark law]

Of course registrations are class specific but he has registered class 37,41 and 42 which is a pretty good catch all for what they do.

 

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While my house ain't at pH standard its close enough for me. In my last pad, a 1960 council townhouse, the air quality was terrible. It was stuffy and generally in winter had damp patches due to the high amount of condensation. The change to what my new house is like now is night and day. No condensation and no stuffy air. My wife always opens the windows to let fresh air in even though I explained that is what the mhrv is doing. Now I just let her work away. People get too wrapped up in trying to make sure your house has no cold bridges and has thick insulation everywhere and airtightness tape on everything. Me I have a large wrap around window that is as big a cold bridge as you could get. Does it bother me, not a bit. It lets an unreal amount of light in and is nice to look out at. I even have two stoves, one pellet and one wbs. I love sitting in front of them on a cold day looking out the big window watching the world go by. 

 

Remember that at the end of the day you have to live in the house when it's done so have nice big windows and even let the wife open them. Enjoy the time you spend in the house instead of obsessing over the minute details that pH requires. 

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11 minutes ago, Declan52 said:

Me I have a large wrap around window that is as big a cold bridge as you could get. Does it bother me, not a bit.

 

As long as you're comfortable with going to hell  :P

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@jack I'm pretty sure the reason for Jeremys property being downvalued by a surveyor, would have been because it's timberframe with timber cladding. 

 

I managed a Halifax agency for 10 years. I was constantly dealing with survey retentions and problems. 

 

Many surveyors want to pass responsibility of any risk to another party. Hence the reason 99% of surveys recommend damp and timber inspections in houses with no evidence of damp. 

 

If they come across a house without a block skin many of the "old school" surveyors just don't like them. They can be quite derogatory with their opinions in my experience.  

 

They also base their valuations on comparable evidence (recently sold local houses). So "non standard" builds cause them a headache. 

 

Their lives are easier if everyone just sticks to building cavity walled houses, hence they don't encourage anything else :) 

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51 minutes ago, Barney12 said:

With the amount of stuff I am guilty of it was never in any doubt.

 

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Looks like I spent £4k on a 4.5m wide, 2.2m high passive cat flap without even realising. Cat has chosen the living room slider as her chosen means of entry and exit.

 

Agree with Jack  - when its very cold or hot out then the windows and doors can stay closed and the house is nice and comfortable, rest of the year I don't really care.

 

Our trades noticed this during the summer - they slowly realised that if they shut the front door & windows early on on a warm day the house stayed cool, if they left them all open, it got too hot. They admitted that it was counter intuitive but obviously worked!

 

We never bothered to get passive certification, seemed like a lot of money for no real benefit.

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9 minutes ago, Sensus said:

 

The honest answer is that we simply don't have sufficient data yet.

 

There certainly is evidence that any form of 'managed' ventilation system, particularly those that operate at fairly low ACH, is a major contributor to 'sick building syndrome', and there are technical reasons that you can't make the very simplistic MVHR systems that are currently available work at the sort of ACH we'd like them to be able to work at for human health and wellbeing.

 

It won't be popular for me to say so on these forums, I know, but PassivHaus is at the extreme end of the design spectrum and it is invariably promoted by people who (whether they see themselves as such or not) are extremist 'fanatics' in building technology terms.

 

I don't mean that in quite the negative way it perhaps appears, and I do support exploration of these construction strategies - it's the only way we'll gain the necessary experience - but I do think we need to be careful not to dismiss such concerns, as they're certainly not unproven or without basis.

 

An interesting reply. I guess the question is; where should the design sit between the fairly poor standard of current regs churned out by the major developers and the fanatical (I think that's a fair description) passive house? 

 

It it seems the low volume market (and especially timber frame manufacturers) want to trade off the ph band wagon. Many do it so they can command premium prices. 

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33 minutes ago, Sensus said:

There certainly is evidence that any form of 'managed' ventilation system, particularly those that operate at fairly low ACH, is a major contributor to 'sick building syndrome', and there are technical reasons that you can't make the very simplistic MVHR systems that are currently available work at the sort of ACH we'd like them to be able to work at for human health and wellbeing.

 

I'd love to hear more about this.  What little I've been able to find in the past suggested that UK regs ventilation rates actually resulted in too much air exchange, leading to unduly low levels of moisture during dry winter months.  

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2 hours ago, K78 said:

@jack I'm pretty sure the reason for Jeremys property being downvalued by a surveyor, would have been because it's timberframe with timber cladding. 

 

 

That may well be the case, but the story Jeremy relayed was that the surveyor specifically told him that "eco" houses, such as Passivhaus standard houses, were worth 10% less because the eco angle put people off.  Nothing about the construction method (although that may have framed - pardon the pun - the surveyor's thinking).


I tried to find the thread over on ebuild, but it's tough given he had nearly 11,500 posts!

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3 minutes ago, Sensus said:

Current Building Regulations new-build  minima are already very strict, compared to the majority of the UK's housing stock, and anyone who pushes beyond them should recognise that they are entering territory into which the leading experts have decided, on balance, that it is unwise to push mainstream development any further just at present.

 

 

Genuine questions: are these "leading experts" all unbiased researchers without links to large builders?  Do you believe that the sole or dominant reason for stopping here is that independent experts have concerns?

 

And while the rules may in theory be strict, do you believe that when a developer builds 10 or 100 or 1000 houses, all of them are built to fully meet the regs?

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1 minute ago, Sensus said:

Certainly, one of the characteristic defects that has started to exhibit itself with houses build to current regs is internal mould growth, which isn't something that happens if your atmosphere is too dry.

 

This is in houses to current regs without MVHR though.  When most of us talk about "beyond regs" levels of airtightness, we're generally talking about implementing MVHR at the same time.  

 

I assume the main concerns with moisture are the interstitial kind, rather than the "black patch in the corner" that you sometimes get on external walls of poorly insulated houses?

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43 minutes ago, jack said:

 

That may well be the case, but the story Jeremy relayed was that the surveyor specifically told him that "eco" houses, such as Passivhaus standard houses, were worth 10% less because the eco angle put people off.  Nothing about the construction method (although that may have framed - pardon the pun - the surveyor's thinking).


I tried to find the thread over on ebuild, but it's tough given he had nearly 11,500 posts!

 

I remember the thread. It sounds like a typical surveyors excuse to a home owner. And a bad one at that. It's crazy to say that the "Eco" angle puts anyone off these days. If anything "Eco" carries a huge premium. 

 

What puts many brits off is the thought of a timber frame with timber cladding. I'm considering it and my parents and many friends think it's odd at best. 

 

Even though its the buyer or builder who usually pays for the survey, the valuation is usually to satisfy the mortgage lender.

Edited by K78

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1 hour ago, Sensus said:

And no, it does tend to be the 'black patch in the corner' kind; not associated with cold spots any longer, but more that you get 'dead spots' in the air circulation which in combination with high levels of relative humidity (moisture from respiration, cooking, washing that isn't sufficiently dispersed by the low ACH ventilation) can facilitate mould growth. We spent a fair while trying to blame thermal bridging before we worked out the true culprit though.

 

In a way, this sounds to be less an air exchange rate problem, and more an issue of internal air paths.  I guess the paths are too difficult to model (especially given the different ways in which people use houses) so the simplest solution is to increase ventilation rates.

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Sensus, I am a bit confused. Or rather quite confused.

 

I lived in 4 houses in the last 7 years. 2 old, c. 1900 solid walls, 2 mid century. Apart from the current bungalow (1950), which is detached and on the slope and for these or some other reason is significantly better, all other houses were a nightmare. Built-in wardrobe to external wall in 1950 semi (that is on the first floor) was full of mould. We had mould on the wall behind a sofa - not even sitting too close to this wall. We still find clothes that we did not use (hence did not need to wash) after moving here 2 years ago and those smell musty. So what I am trying to say is all these badly insulated houses with "healthy internal environment" did not in fact feel healthy at all. At the same time I am pretty certain those who have UFH will not get mould on their properly insulated walls. When we compare leaky vs airtight shouldn't we look at the share of each type suffering from such problems? 

Edited by oldkettle

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Interesting discussion. Scary, but very interesting!

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16 minutes ago, Sensus said:

You're making the assumption, I think, that there is only a single mechanism at work causing the problem.

 

That's why I mentioned the problem of loft condensation, which is a parallel in many ways: yes, you get loft condensation as a result of interstitial condensation from air leakage in older houses, but you also get it as a result of dewpoint and surface condensation in new ones. There's a happy medium between the two where it's not a problem.

 

Yes, you get mould growth as a result of surface condensation in poorly insulated older houses, but you also get it as a result of moisture build up and poor air circulation in very airtight new ones. Again, there's a happy medium to be had where it's not a problem.

 

Simples. :)

 

I'm a big fan of happy mediums: you'll usually find that there's a good reason that extreme design solutions lie at the extremes. ;)

 

If I am not mistaken you are replying to me :-)

 

If so, I hope I have made no assumptions. I just asked to compare the percentage of houses with problems between well insulated and poorly insulated - since you clearly have more experience and stats available. And if you have a separate set for "happy medium" category - for those as well, as long as they are not defined as "houses with no problems" :-)

 

I am a big fan on 80/20 principle but I don't know where 20 lies in building technology. 

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2 hours ago, Sensus said:

 

With the very limited and localised vents provided with MVHR, it's impossible to guarantee decent and reliable levels of air circulation to all parts of all rooms without increasing ACH rates

 

Could you post a reference please.

 

In an occupied house with people moving around, doors being opened and closed, convection currents and the MVHR extract and return vents I would naturally have considered the internal air volume to be well mixed, but you seem to be suggesting that with even with a theoretically sufficient ventilation rate from the MVHR unit, you could still get poor circulation to such an extent that localised areas of high RH could cause mold growth.

 

I'd like to understand better the mechanics of how that could occur.

 

Edited to add:

Just did a little calculation, it would need the RH to sit at +80% for a week to promote mold growth in a typical PH insulated home, if there were no cold bridging issues causing a cold spot that brought the temperature of the internal face of the wall below what you would otherwise expect.

Edited by IanR

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I got that loft condensation in a house I built. Exactly like you say customer wasn't happy about their 3tonne of possessions up there getting wet. Was just forming on the north elevation underside of breathable roofing felt and trusses. 

 

it was ventilated both sides at eaves level but we went back and put 3/4 vent tiles up high on the cold side and it managed to sort it. 

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52 minutes ago, Oz07 said:

I got that loft condensation in a house I built. Exactly like you say customer wasn't happy about their 3tonne of possessions up there getting wet. Was just forming on the north elevation underside of breathable roofing felt and trusses. 

 

it was ventilated both sides at eaves level but we went back and put 3/4 vent tiles up high on the cold side and it managed to sort it. 

 

Extra ventilation can definitely reduce this. I had a big condensation problem in my loft (retro fit insulation, no ventilation) and simply cracking open the skylight has made an enormous difference. I will eventually add some high level vents as well when I have some time.

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Interesting topic

 

My previous 1930's 9" solid brick house had condensation issues on the cold walls, most notably in a built in wardrobe on an outside wall, only "solved" by leaving the wardrobe door permanently open in the winter so it didn't get so cold in there (sliding doors can be left open without getting in the way) but I never had issues in the loft.

 

Present house is 2003 built timber frame to standard (at the time) methods, 6" insulated frame, 300mm loft insulation. I have never seen any condensation or other issues in the loft.  which is perhaps surprising as I know the loft hatch is not well sealed.  In fact this house is a very dry house in all respects, no condensation problems anywhere not even on windows or mirrors in bathrooms.

 

My new house will have even more insulation, and the thing missing from the present one, attention to detail to get the air tightness better and mvhr.  The new house is also built with a warm roof so any loft space will be warm and inside the sealed envelope of the house.

 

Perhaps warm roofs are the answer, and from my own experience I can't see them as being vastly more expensive.  Yes it will use more insulation as you have to insulate a larger area, but it makes air tightness detail a LOT easier.  In fact having embarked on this warm roof detail, I now find myself when looking at the cold rof in a new build I am currently wiring thinking "gosh the detail of this roof and it's insulation is absolute rubbish"
 

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22 minutes ago, Sensus said:

I can't off the top of my head; I don't keep copies of every single report I read

 

Anything Google can find for you will be OK with me.

 

I've found several large scale studies into MVHR systems in domestic homes, and most are critical about sub-optimal performance of poorly maintained systems or occupants unfamiliar with the correct use, but none comment on the phenomenon you mention, which is odd as it would be quite a serious failure.

 

26 minutes ago, Sensus said:

The easy way to visualise MVHR is like a light:

 

No, not really. Eddy currents for one will be caused around any sold objects, nothing like light.

 

I'm certainly not convinced about the potential of mold growing within the thermal envelope of a PH-level insulated home. RH would need to be too high for too long, due to the temperature of the internal faces of exterior walls and even windows.

 

Within the cavity, or outside the thermal envelope, if there is poor detailing, is another subject.

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33 minutes ago, Sensus said:

To answer your question, I no longer have the stats available to me. I could have answered you, with a little research, from the customer care files at the last major housebuilder I worked for, And, indeed, in at least three instances that I recall, I prepared colour-coded plot-plans on sites where we were getting lots of reported problems, in an attempt to identify a pattern to the problem. I no longer work for them, and I no longer have access to my old files. But from recollection, I would say that the figure was perhaps somewhere between 7-15% of properties with reported problems. I'd personally say that 80/20 would be unacceptable: I can't imagine even the most cowboy developer being happy with anything like a 20% defect rate!

Just wrote an answer that disappeared on posting :-(

 

It was late and I was in a rush. I was referring to "20% of men drink 80% of beer". 20% of effort deliver 80% of result. To me it sounded similar to your happy middle ground : do enough to solve most of the problems. 

As per cowboys I am afraid they do create 80% of all defects :-) and not necessarily because they are happy with it but because they can not do any better.

 

Back to the topic. In winter when it's raining the humidity easily reaches 85% inside even when the house is properly heated. Opening windows does not help. With MVHR humidity does not seem to reach that level hence my expectation of a much better outcome even for these corners where I agree there may well be little air movement.

 

It is quite possible the difference of opinions comes from the angles : you look at results of major builders and I fully expect these results to be bad. The others look at results of specialist builds. My pet hate is the fact that builders were allowed to practically become land merchants: buy in bulk, split to tiniest strips, build anything - profit. If they were just builders, producing what the customer wants, there would not be garages that can't fit a car.

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1 hour ago, Sensus said:

 

The other potential issue is that warm roofs only make sense when you use the roof space as habitable room, and Planners will take some convincing that room-in-roof construction should become the standard, across the country for all development, when in many areas it's not a traditional form.

 

Is that first half actually the case when the needs of the homeowner are now so much more flexible? Is there actually much downside?

 

Any house I lived in even on my own would need a spare bedroom and an office as a minimum, and intergenerational households (or shared or HMO or friends) are becoming more common - which is like a return to pre-1970? We need teh flexibility.

 

If I don't need a room, in a properly built house the extra heating is negligible, and I (or the developer) can recover the expense because we buy houses by the number of bedrooms.

 

People in the country in France seem to just just close the door to the top floor if the children have left, and stay in the same place.

 

Is the problems you discussed previously on stagnant spots with MVHR an argument for relooking at ducted warm air heating as used to be around in the 1960s/1970s? Say using the heating element in traditional PH MVHR systems but giving it more oomph and perhaps more distribution?

 

Ferdinand

Edited by Ferdinand

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