Overheating – how can we avoid it? – article from Green Building

This article originally appeared in Green Building, Spring 2014

“Everybody loves the summer time”, as Carole King once sang: everybody that is, except those who are separated from their sweethearts – and those sweltering in stifling buildings that they just can’t get cool.

At its worst, overheating can be a serious – even fatal – health issue, with the very elderly, and babies and small children most vulnerable, and heart attack, stroke, and sudden infant death all possible consequences. But much more commonly it is a discomfort issue, which can affect the usability of buildings, and/or drive people to deploy energy-consuming measures such as artificial cooling.

A building that cannot be cooled down to a comfortable temperature whatever you do is obviously overheating. One that cannot be cooled in a secure and comfortable way (eg, can only be cooled via opening window onto a busy road, or by leaving patio doors open at night), overheats so far as the occupants are concerned. Both are a failure on the part of the design and construction team.

How hot is too hot? The occupant has the last word on this, but designers do need guidance on what ‘most occupants’ can cope with:

As the National Housebuilding Council reports, work by CIBSE and Arup suggests that most people begin to feel ‘warm’ at 25ºC and ‘hot’ at 28ºC. At 35ºC “there is a significant danger of heat stress.” Heat at night bad enough to interfere with sleep seems to compound the danger to health.

In practice, comfort also depends quite a lot on humidity (which determines how readily people can keep themselves cool via sweating) and air movement (ditto) .

In general, it ought to be possible to avoid overheating without sacrificing winter time comfort and energy efficiency. Despite a warming climate we’re still going to want houses (in the UK) warmer inside than out, most of the year. Continue reading

Does Natural Ventilation Work? – References and Links

I’ve had a couple of requests for links to the sources for “Natural Ventilation – does it work?”, my article for Passive House Plus Issue 6 (start of 2014), so here is a list of most of them – live as at the time of posting in April 2014, but no guarantees they will remain so of course.

My apologies where (a few) refrences are behind a paywall – it usually means either that I’ve wriggled my way behind it somehow (though if your subscriber-only publication is on here, not yours, obviously 😉 ) – or a helpful academic has supplied me with a copy. Or alternatively, it means that I’ve only referred to the abstract.

The references are roughly in order of their appearance in the article. Here you go:

The NHBC Foundation’s commendably honest account highlighting a string of concerns in the design, specification, installation,  commissioning and operation of MVHR systems in 10 ‘zero carbon’ homes: Assessment of MVHR systems and air quality in zero carbon homes NHBC Foundation August 2013 (Greenwatt Way study) http://www.nhbcfoundation.org/Researchpublications/MVHRsystems/tabid/585/language/en-US/Default.aspx (NB you have to register to download this, but registration is free)

Neil Jefferson, director of the NHBC writing in Building magazine, questioning whether MEV, PSV or natural ventilation are exempt from the performance issues that NHBC uncovered with (non-Passivhaus) MVHR installations in the study above: http://www.building.co.uk/we-need-to-know-all-ventilation-systems-are-safe/5062555.article

Bob Lowe’s 2000 modelling study investigating the “under-ventilation index” for naturally ventilated dwellings (the proportion of the heating season for which a dwelling will be underventilated without additional window opening). His results suggested that even for leaky buildings that lose heat unnecessarily in very cold or windy weather, and are generally over-ventilated (draughty!),  under-ventilation for a proportion of the time (in mild and/or still weather)  “is almost assured”: Building Services, Engineering, Research & Technology 21 (3) 179-186 R. J. Lowe: Ventilation Strategy, Energy Use and CO2 Emissions in Dwellings – a Theoretical Approach http://bse.sagepub.com/content/21/3/179.abstract (abstract)

Simon McKay & David Ross (AECOM), and Ian Mawditt & Stuart Kirk (Building Services Ltd) carried out a small study (of 22 homes of different types)  for DCLG, to investigate whether Part F 2006 was providing adequate ventilation and IAQ in homes, and whether it should be uprated at the review in 2010. They found that all of the flats and 40% of the houses failed to achieve the recommended background ventilation rate; NO2 and volatile organic compound levels exceeded guidelines in a number of dwellings – and this was with all vents open and fans running. When the researchers arrived however they had found 60% of vents were closed and many extract fans disabled. Six of the 22 households didn’t use their kitchen and bathroom extract fans at all, and five said they used the isolator to control some of their fans  – though in fact many more actually did so: Ventilation and Indoor Air Quality in Part F 2006 Homes BD 2702 DCLG 2010 http://www.scribd.com/doc/43637758/Ventilation-and-Indoor-Air-Quality-in-Part-F-2006-Homes, and  Ian Mawditt’s  presentation on the findings, showing the position of vents and fans as normally used by occupants http://www.goodhomes.org.uk/downloads/members/ian-mawditt-operation-and-behaviour.pdf

Stirling Howieson of the University of Strathclyde has reported on the basis of his recent research that “technical standards prescribed by the Building Regulations are not being enforced”. He also found that natural ventilation tends not to be used as intended and fails to give good IAQ. Howieson and colleagues looked at 24 new-build homes constructed to  2010 regulations, where trickle vents in the windows provided the only source of background ventilation.  CO2 levels measured in occupied bedrooms “were found to be at unacceptable concentrations” (occupied mean peak of 2317 ppm with a maximum of 4800 ppm): “Are our homes making us ill?”, Stirling Howieson, University of Strathclyde. Perspectives in Public Health 2014 in press, abstract at https://pure.strath.ac.uk/portal/en/publications/are-our-homes-making-us-ill%280b8ce07f-b36d-499f-8caa-08c249f241ac%29.html

Derrick Crump, Sani Dimitroulopoulou and colleagues at BRE carried out a study of ventilation and indoor air quality in 37 homes in 2002;  although the sample were approximately as leaky as the average stock,  the majority (68%) of the sample had below the recommended design air change rate of 0.5 ach. And some suffered indoor air pollution issues: in winter 18% of the homes during winter had kitchen CO levels above WHO guidelines, and even in summer, 13% of them did.  In winter the kitchens of six homes also exceeded NO2 guideline values: VENTILATION AND INDOOR AIR QUALITY IN NEW HOMES Crump, Dimitroulopoulou et al BRE, Watford, http://www.umad.de/infos/cleanair13/pdf/full_104.pdf. The study is also summarised here

A Good Homes Alliance report presenting examples of good ventilation practice in low energy homes highlights only a few projects with natural ventilation (three with vents plus humidistat-controlled extract, two with passive heat recovery, and one with a passive stack system). Even so, two of the six dwellings had had poor IAQ , which was attributed to occupant behaviour: in both cases, occupants said they had closed vents/shut off fans because of noise or draughts. IAQ was poor in both cases.  (Air quality in the other four of the six naturally ventilated dwellings was good): http://www.goodhomes.org.uk/downloads/news/VIAQ%20final%20120220%20-%20PUBLICATION.pdf

Contrary to general expectation, buildings may become more airtight as they age – which may also present an issue for ventilation design recommendations. In one NHBC study,  eight of 23 homes became more airtight 1-3 years after completion. And in the NHBC’s Greenwatt Way study (see link above), 9 out of 10 homes became more airtight. http://www.insidehousing.co.uk/eco/room-to-breathe/6514729.article

Some research suggests that in order to reduce the risk of house dust mite problems (mites are known to exacerbate asthma in particular) relative humidity below 60, or even lower, should be sought: Lawrence Berkeley National Laboratory, http://www.iaqscience.lbl.gov/dampness-impacts.html


Healthy buildings – feature in Green Building magazine

Most people spend 80 – 90% of their time indoors, which means the indoor environment is where people meet many of the influences that affect their health and wellbeing, for good or ill. The impact is serious: just one condition affected by the indoor environment, asthma, kills three people a day and costs the country millions of pounds annually.

We all want the buildings we create and  occupy to be healthy, and the sustainable building world often makes special claims to be creating healthy spaces. But are we directing our attention the right way? Which hazards are most important – and which can we actually do anything about?

In this article for the Spring 2014 issue of Green Building magazine, I have a look at the indoor hazards that might affect out health, and consider which ones we can do anything about – and how they might be tackled.

Download the article in pdf, for references and links: Healthy Buildings

Natural ventilation – does it work?

While mechanical ventilation is sometimes perceived as problematic, expensive and possibly even energy-guzzling, natural ventilation often seems to be seen as – well – “natural” – a safe, old-fashioned,  reliable default solution. In this article for Passive House Plus I had a look at this assumption.

Theoretical modelling suggests that natural ventilation is likely to be rather unreliable, with the same building at risk of both under- and over-ventilation under different weather conditions. But what happens in practice?

The first problem I had was finding some data: there is very little of it.

In the studies I was able to find, it turned out that indoor air quality in naturally ventilated homes (including levels of relative humidity, oxides of nitrogen, and volatile organic compounds, for example) is not what it should be. (I also found some studies from schools raising similar concerns, but there wasn’t room to write about these as well).

For example, a study of 22 homes built to the 2006 Part F regulations for ventilation found that about half of them failed to achieve their recommended background ventilation rate even with all vents open/fans running as intended; pollutants exceeded the guideline levels in a number of them.

But what was really worrying was that when the researchers first arrived, they found that many of the vents were closed, and many of the extract fans (both in bathrooms and kitchens) had been disabled at the isolator. Similar findings appeared in all of the studies I was able to track down.

Unfortunately we do not seem to be very sensitive to the high relative humidity and other pollutants than are, nonetheless, dangerous to our health – but we are sensitive to draughts, and noise. This means that vents get closed and fans shut off, and our living conditions are unhealthier than they should be as a consequence.

What was interesting was to find that poor indoor air quality is not a new problem; studies dating back to long before airtightness was much of an issue, showed similarly poor indoor air quality and low ventilation rates. So the comfortable belief that natural ventilation is somehow “tried and tested” probably needs revisiting.

We seem to be facing a ventilation performance gap as worrying as the energy performance gap. As with energy performance, designers seem to have checked compliance with the Part F recommendations, looked at the results from their modelling exercises, and assumed this means a building is going to be properly ventilated in practice. As with energy performance, monitoring data shows this just isn’t the case.

At least the energy performance gap is now on the agenda – and we are even getting some practical solutions discussed. But despite the huge costs to the nation of respiratory diseases like asthma, and numerous other ailments worsened by poor air quality, ventilation is too often taken for granted. It’s probably time this changed.

 Read the article in pdf here Natural ventilation – does it work?

My thanks to Passive House Plus for the use of this document.

I have now added a post containing links to a number of the references used in this article, here.


Passive House goes large

Passivhaus is no longer just the preserve of the self-builder: more and more large Passivhaus schemes are being announced. These include both non-domestic buildings, for example in schools and universities,  and multi-housing schemes, generally in the social rented sector, though sometimes with a portion for private sale.

In this article for Passive House Plus magazine I looked at some of the economies of scale available on larger Passivhaus projects, and some of the obstacles that larger schemes may run into. Also, following from my previous article on the cost of Passivhaus, I looked a bit further into the economics of Passivhaus from the point of view of developers and owners – in both the domestic and the non-domestic sectors.

Read the article in pdf here: Passive House goes large

My thanks to Passive House Plus for the use of this document.

The cost of building passive

Passivhaus (Passive House) is often thought of as being “too expensive” for the mainstream. There are some designers and developers however who are managing to shave the capital cost premium down to just a few per cent – or even zero.

In researching this article for Passive House Plus I learned that the extra costs, where they are incurred, seem to derive from two main sources:

  • Passivhaus components tend to be more expensive than the “conventional” alternatives – though this difference is diminishing all the time; and
  • There is a “learning curve” in first (and probably second and third) Passivhauses for any team, where designers and contractors alike need to spend a bit longer working out how to co-ordinate their activities to ensure that details are buildable, and that built quality matches up to the standards sought.

The extra costs are mainly up-front; looked at over the building’s first decades of lifetime, running cost savings – including maintenance, and even cost associated with tenant dissatisfaction – start to pay back the initial investment. Continue reading

Why I think retrofit needs to move off energy bills and on to general taxation

Like many others, I am horrified that the government has scaled back aspects of the Energy Company Obligation mid-programme. You can read about some of the immediate, alarming consequences of this in a report from Inside Housing here.

However, as I’ve said before, it seems to me that long-term  it makes little sense to restrict the national retrofit programme to what can be funded via a charge on energy bills. In summary, this is why:

  • Retrofit is about more than energy bills, it’s about health, education, social welfare and common decency. And about energy security and cutting emissions.
  • Because of the state of our housing and therefore, the scale of the need, a high spend is required.
  • Because of the scale and the range of the benefits, a major retrofit programme would bring tangible revenue savings to a range of bodies such as those tasked with improving economic, health, social welfare and educational outcomes, and delivering on our carbon targets.
  • Paying for retrofit through energy bills is regressive, hitting the poorest proportionally hardest, even at current spending levels.
  • The scale of the spending needs to expand many-fold. This would ramp up the regressiveness. In effect, every household, including the poorest,  would be paying a substantial chunk of the costs for NHS, social welfare etc via their energy bills. This is not only likely to be politically untenable, it also undermines the accepted approach to progressive taxation in this country.
  • The creation of a third party obligation, ‘leaving it to the market’ to decide what to deliver on the basis of a very simplified understanding of costs and benefits, cuts informed stakeholders out of the equation. It excludes them from them any meaningful say over priorities, responsiveness to changing needs, and quality of interventions.
  • It also ignores the ‘beneficiary pays’ principle: health, education and welfare budgets would all benefit considerably, on the back of bill payers.

*The ECO recognises only two parameters of benefit, presumed carbon savings (calculated via RdSAP), and “affordability” again, calculated via RdSAP.


Allowable solutions – who are they trying to kid?

This is by way of an open letter to DCLG – which I sent as a covering letter to my response to (questions 1&2 of) the allowable solutions consultation – see previous blog

“I believe the whole idea of (1) “zero carbon” and (2) defining this or any standard not by how well the subject of the standard performs, but how many other people can be bribed to perform well on its behalf, is dreadfully misguided.

If you want to reduce the carbon emissions from new homes, then reduce the carbon emissions from new homes. Don’t reduce them some of the way to your target, then faff around erecting huge, complicated structures to reduce emissions from sectors other than new homes, and then pretend to yourselves and the world that somehow the new homes are low or “zero” carbon. Manifestly, they are not. What a colossal waste of effort!

If it isn’t possible, practicable, or affordable to make a new home zero carbon on-site (and it almost certainly isn’t) then for heavens’ sake don’t carry on pretending to yourselves or anyone else that it is. As you have found, the pretence requires a positively rococo structure of pretend emissions savings – your “allowable solutions” —  cumbersome, inconsistent, full of internal contradictions, and beset with potential loopholes.

And worse, what a colossal diversion of yours and the industry’s precious time and energy. All this effort going into refining the way you will trick out this delusion with regulations, price caps, verification procedures etc etc, when:

a)     the net impact on carbon emissions overall will be minimal (how can you ever know an action is truly additional, especially if people are competing for the cheapest actions – which, naturally, would be the ones most likely to happen anyway), and;

b)     you are incurring a huge opportunity cost in terms of effort, time, expense, and individual and corporate head-space – meaning the impact on emissions from new homes will probably be to INCREASE them relative to what they could have been, had you and your predecessors focused on reducing home energy in the first place.

Although mass housebuilders are notoriously uninterested in producing a high-quality product, seeing as they can sell what they produce anyway, given the housing shortage prevailing in this country,  some landlords/developers are now starting to take an interest in delivering really high quality homes. A significant number in the ‘affordable’ and social rented sectors, and now some building speculatively for the private market, are building or actively planning to build to the Passivhaus standard (the low energy standard I happen to know about). They are opting to build to truly low energy standards not because of any leadership from DCLG, but because they think it’s a good idea for users/purchasers, and it is possible to make it stack up financially, especially after the first one or two builds have been completed.

They don’t have any special trick, other than the right attitude. If they can make it work financially, then so can the big housebuilders. Perhaps the big housebuilders don’t want to change their ways, perhaps because their business model is based on shoddy workmanship. But the Zero Carbon Hub has told us this has to change anyway, to reduce the performance gap.

If the big firms adopted very low energy design, the marginal cost would fall considerably, as components would drop in price. And of course if all housebuilders were under the same obligation, then there would be no competitive disadvantage. (Your impact assessment cites a theoretical disadvantage versus older homes, but your own research suggest this is a diminishing effect, given that old homes are cold and/or expensive to run until they have had money spent on them, and I mean proper money, not just a Green Deal’s worth.)

I’m not saying this could happen overnight – it would of course take some time to build the expertise. But in what way is this not a desirable goal? How would using less energy not be more desirable than simply wasting energy (by building worse buildings than you could do), and getting someone else to produce some more low-carbon energy somewhere else – or getting them to save some energy that they should be saving anyway?

Given that ultra low energy homes (and buildings of all kinds) are desirable, feasible, affordable and indeed necessary, there isn’t any excuse for not starting out now on a clear path to bring all new homes to a proper truly low energy standard, delivered via the fabric, so it’s built in.  Zero Carbon and allowable solutions are by contrast an unforgiveable diversion up a blind alley.”

Allowable Solutions Consultation – silly policy, but still worth responding

Plenty of scorn has been poured on the way that the zero carbon homes target has been watered down, then watered down again, as if it were a homoeopathic remedy for climate change.

Others, notably Nick Grant and Doug King, have led the charge against the very concept of zero carbon buildings as being an illogical concept that diverts construction from what it could be doing best — and I cheerfully count myself among their followers.

However, on the particular point of the current government consultation on the Allowable Solutions element of “Zero Carbon Homes”, I do think it is worth engaging – as there is an opportunity to make the arguments that high fabric standards should be at the heart of the zero carbon policy. Who can say how long the Zero Carbon Homes policy will last? – however, the better the fabric standards we have at the core of it, the better placed we’ll be to replace it with something more sensible.

I have had a look at parts of what DCLG is consulting on, and describe and comment on what I found, in the article below.

Download Article on Allowable Solutions Consultation October 2013 (pdf)

The article also contains the links to the DCLG consultation documents.

STOP PRESS! Doug King has shared his response to this consultation, making the case very thoroughly that “offsetting” energy use and carbon emissions from housing, by reducing energy use and emissions in other sectors, is a nonsense. Those other sectors should be making those cuts anyway – all selling them off as “allowable solutions” does is to pick off the low-hanging fruit from another sector, making it more expensive for them to do what they need to do. The net effect would probably be to reduce energy use an emisissons LESS than you would if proper energy and carbon standards were applied to housebuilding in the first place.

Read his response here:







The Green Deal and the ECO

This article, originally pubished in Green Building Magazine (Spring 2013) is the second part of my look at the Green Deal, and considers whether and how the Energy Company Obligations (ECOs) might work, and whether and how individual contractors and householders might be able to take advantage of them to help install solid wall insulation, in particular.

I concluded that it was quite unlikely that most private SWI intallations (outside of some defined areas/categories of deprivation) would qualify for 100% funding, because the energy companies will be chasing the cheapest “carbon points” as calculated in SAP – but useful grants might be available for households who were keen enough to fund the difference themselves. It was also not yet clear how smaller and independent contractors might secure ECO funding for their customers, and thus, work for themselves – however, various avenues look possible.

In short, the ECOs should offer some help to some people, but are far from bridging the yawning gap between what the Green Deal can achieve (rather little, see previous article on the Green Deal) and the 80-odd-% cut in energy consumption/emissions that we desperately need to achieve. I suggest that as energy efficiency benefits building occupants, public services (notably health & education), the benefits bill, energy security and the cost of energy, and the balance of payments,  then perhaps all these benefiting entities and sectors should be contributing in a co-ordinated way.

View/download The Green Deal and the ECO (pdf – version without illustrations)

And here you can download a pdf of Green Deal and the ECO as it appeared in the magazine, complete with illustrations.