Health risks associated with passive houses

[Mikey_1980]

We have been living in our new house for around 3 months and I feel the air quality is a lot better than our old house. The people who supplied and installed our MVHR were very thorough in the design and commissioning and advised us to check the filter man every two months for for the first 6 months and then every 6 months after that. We also have many rooms with two inputs to make sure we are getting a good flow rate of air through, and they marked all the doors up for where they needed to be cut by our carpenter to make sure the flow of air round the house was adequately I think it is all down to making sure MVHR is well designed/installed and maintained.

[ProDave]

45 minutes ago, Sensus said:

Unfortunately, major housebuilders don't like to put themselves at a commercial disadvantage to their competitors by being the first to adopt any measure that results in even a slight increase in costs (I'm still scarred by the arguments I had with my ex-boss over increasing the size of our garages by a brick or two, so that you could actually fit cars in them!). If it happens, it will probably have to be driven by mandatory changes to the Building Regulations.

 

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.

 

I agree, and for some time I have always thought major house builders are out of touch with what most people want (either that or what I want is so different to the average buyer?)  That is one reason why I self built the last house and am self building the new one as so much of what I see the mass house builders churn out just does not appeal to me.

 

Up here most houses are at least partly room in roof, so part of your sloping roof has to be insulated as a warm roof so to me it just seems daft to make the little triangle at the top a cold roof and not just make the whole thing a warm roof, but that little triangle of cold roof is what most builders still do.

 

[Stones]

I take the point about making building regs ever more stringent - insulation levels do reach a tipping point where the cost far far exceeds the benefits, but to policy makers, you can see the attraction of the passive house model, a house that doesn't need heating - great, we get rid of fuel poverty and reduce our carbon emissions.  

 

The biggest problem as I see it is the inspection regime (or lack thereof).    You can see the attraction to developers - why spend £2 - £3K testing a house and having to install an MVHR system when you can use a default air permeability value and simply get away with trickle vents and a few cheap extraction fans.

 

The vast majority of people I have spoken to see trickle vents as nothing more than a source of unwanted drafts.  Likewise extraction fans, they view them as noisy.  Nobody really stops to consider the impact of closing vents or switching fans off, they just go ahead and do it, then wonder why problems develop.  It's not much of a leap to suggest the same would happen in a PH house with someone not interested or acquainted with what is needed.  MVHR units get switched off because the householder is told / believe it is costing them money, they fail to check and replace filters, they refuse to increase ventilation rates etc. 

 

I did a bit of experimentation in our last house with ventilation rates.  Day by day, I gradually reduced ACH to building regs minimum and then slightly below.  The result was a fairly unpleasant internal environment and condensation forming on windows.  Increasing the ACH got rid of these problems and led me to conclude that the prescribed minimum ACH was simply too low a rate to properly deal with all of the consequences of modern day living (especially drying laundry inside and daily showering).  

 

As every house (even when it has the same design / layout) will perform differently according its location, occupancy etc it stands to reason that every house has to be tuned / managed to meet the specific needs of its occupants.  The only way of doing that is by trial and error, seeing what works and what doesn't.  That brings us back nicely to the end user.  If he or she is interested and prepared to go through that process, then they will have a very comfortable and pleasant house to live in.  If they aren't interested, then their surroundings will always be a compromise and in some cases develop into some of the problems referred to earlier.  Not an easy one to solve as no matter what handover information is given, some end users will choose to ignore the advice they are given.

 

I for one, wouldn't even consider building a house without having MVHR installed.  I'm currently renting a house without adequate ventilation and it is horrible.  Properly managed (including getting the right rate of ventilation) there is in my view nothing to beat a well insulated and airtight house.

 

 

[ProDave]

4 hours ago, Sensus said:

 

I think we need to be realistic about the difference between what people want and what they can afford.

 

I assure you  that the major housebuilders are certainly not out of touch with what people want, but they're also very much conscious of what people are willing and able to pay for. If they thought that there were enough people willing to pay for PassivHaus dwellings (with big garages ;)), at commercially sustainably prices, then that's what they'd be building.

 

 

Let me give you some examples of what I mean by "out of touch"

 

My first house was a horrible little 1 bedroom "starter home". Fair enough I bought it because it was all I could afford, literally the cheapest house on the market in the county at the time. Fair enough it served it's purpose. But even that I had to choose carefully. they took 1 design and replicated it across the whole development. That meant some houses had a living room facing north. Absolute madness.  Parking for that development was a communal car park at the end of the row of houses. I hated that for security and difficulty if you want to work on your car.

 

So next house I wanted better.  But all I could find with new houses was more of the same, just slightly bigger houses.  It would have been so easy to do away with the communal parking, make each plot just a little bigger and give each plot it's on site parking space and still have the same number of houses but they just didn't so that.

 

And then throw into the mix you want a garage, well if you do find one it would be tiny, and the only other parking would be in front of the garage.  Don't even get me started on wanting to park a caravan, and a trailer.......

 

I solved that issue by buying a 1930's semi on a corner plot with it's own drive and plenty of space to park whatever I wanted, space for a decent sized garage and space to in fact extend the house and double it's size, all for the same money of a mass builders shoe box site.

 

I guess we have been lucky with our self build plots that they have both been very wide, though not particularly deep plots so have the flexibility for all that we want.

 

[oldkettle]

2 minutes ago, Sensus said:

 

 

I think we need to be realistic about the difference between what people want and what they can afford.

 

I assure you  that the major housebuilders are certainly not out of touch with what people want, but they're also very much conscious of what people are willing and able to pay for. If they thought that there were enough people willing to pay for PassivHaus dwellings (with big garages ;)), at commercially sustainably prices, then that's what they'd be building.

 

The reality is that the self-build market is an interesting curiosity, but it has no real impact on the UK housing market: self builds represent only about 6% of new builds, and new builds only represent 0.5% per year of our housing stock... so simple maths suggests that new self builds represent 0.0003% of the UK market, annually.

 

And, of course, only a tiny fraction of that 0.0003% of the annual market are PassivHaus, whether certified or not.

It is funny you should say this.

 

My understanding is - and do correct me if I am wrong - that the reason the self build is not more wide spread is simple : land availability. Unlike US, where very often developer gets the land ready and then each individual project is agreed per client - here there are only standard boxes being put together to maximise profit. I do like market, what I don't like is the regulation that makes it possible to stifle the market. And the land is a prime example of the result of such regulation. Here in the South East the land is often more expensive than the house that stands on it. I do not believe for a second that people who pay 600K+ for a standard projects would not have paid extra 25-50K for a better quality or a larger size. It does not cost that much at all to make things substantially better (note, not perfect), but the first step is preventing builders from being the only owners of the land available for housing. 

[ProDave]

4 minutes ago, Sensus said:

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.

 

 

I disagree.  I lived in Oxfordshire for the first 40 years of my life.  I only recall two building plots coming on the market with estate agents in the time I was a home owner.  I would love to have bought a plot and built a house then, but it seemed the only way was to buy a plot with a house on it, knock it down and rebuild, so the plot alone has cost you "complete house" money.

 

It was a breath of fresh air moving to the Highlands where bare plots are always on the market with agents and it is so much easier, indeed considered pretty normal, to buy a plot and self build.

 

[Crofter]

I don't have the figures to hand, but I believe that the UK is way behind many other countries when it comes to the proportion of houses that are self built.

[tonyshouse]

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 BUT this would cool the tiles and any condensation would drip onto the sarking membrane and not get into the loft.

 

I strongly disagree with the notion that leaky homes are good, they waste heat, the ventilation is all but zero when it is not windy and way too much when it is windy.

 

it is in my opinion very unlikely that cool damp air coming into a loft from outside could cause problems (all houses would be in trouble if this was the case)

 

re MHRV -- as this runs continuously the air in a house tends to even itself out and there atr rarely problems, very bad areas of thermal bridging could conceivably gather damp and mould, design out thermal bridges would be a better answer.

[Stones]

53 minutes ago, Sensus said:

 

I have to say that I'm increasingly uncomfortable with the whole concept of PassivHaus, as it relies on a premis that assumes minimal intervention or control over the environment by its human occupants.

 

 

I would certainly agree that the premis of house occupants not controlling their environment / fine tuning to their specific requirements will lead to problems, be they poor air quality, mould or whatever. But to change attitudes, you have to start somewhere.  Are the problems  / potential problems that have been raised a good enough reason to halt progressive improvements to building standards?  As we've already discussed, problems exist in existing stock for the same reason - occupants are either unwilling or unable to manage their home to its optimum level of performance. 

 

1 hour ago, Sensus said:

It should also be stressed that policymakers are NOT promoting PassivHaus; it's largely the 'fanatics' of self-build community that are doing that. The policymakers are actually (and quite rightly, IMO) being a great deal more cautious in their approach.

 

How would you define the 'fanatics'?  Reading through this topic, I don't think any of us here are paid up members of the passive house fan club, but we have chosen to take what we individually see as the best elements of passive principles ( insulation, air tightness) and incorporate them in our own builds.  Is there a particular body or group that you feel has unduly influenced policy making?

[Stones]

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.

[K78]

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. 

 

[oldkettle]

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.

[IanR]

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.

 

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.

[ProDave]

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.
 

[oldkettle]

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?

[Ferdinand]

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 October 8, 2016 by Ferdinand

[Stones]

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.

[ProDave]

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.
 

[Ferdinand]

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 October 8, 2016 by Ferdinand

[SteamyTea]

I found moving from Hertfordshire to Cornwall improved the air quality in my home. 

 

Good only wikipedia has this to say about the fraction of air actually changed:

https://en.wikipedia.org/wiki/Air_changes_per_hour

 

I have heard this figure quoted before.

[worldwidewebs]

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. 

[Crofter]

23 minutes ago, worldwidewebs said:

 

Couldn't disagree more. 

Whoosh....

[Ferdinand]

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 October 9, 2016 by Ferdinand

[Oz07]

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

[Ferdinand]

@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