Deep retrofit – the big prize?

Simple home energy efficiency improvements (such as new boilers, cavity wall insulation etc) can bring valuable comfort and health benefits to the occupants of inefficient homes – especially those in fuel poverty – as the last article revealed (see here). However, energy, carbon and bill savings tend to be modest, rarely topping 15% or 20% – and sometimes energy use actually increases!

If housing is to contribute its share of the 80% cuts in carbon emissions this country is committed to, in order to play is part in tackling climate change, retrofits will need to go deeper – a lot deeper. But will occupants benefit from the extra work? And is it affordable?

In the first part of this article we looked at the damage fuel poverty and cold homes do to occupants’ health, and found good evidence that when these twin evils were tackled, occupants could enjoy measurable improvements in their health. Encouragingly, some local health bodies are recognising this and investing in home retrofit to help improve people’s health.

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Ventilation – presentation for AECB

Slides from my presentation to the 2014 AECB annual conference on ‘Natural ventilation – does it work?’.

Download pdf – Natural Ventilation – talk for AECB 2014

Cold bridging, condensation & mould CSE

Failure of ventilation? Photo courtesy of the Centre for Sustainable Energy

For my article on the same subject, see this link:

Natural Ventilation: Does it Work? Article for Passive House Plus magazine

 

Overheating – how can we avoid it?

Jump straight to article in html Overheating – how can we avoid it?

There is a lot of concern that modern, airtight, well-insulated buildings might be more prone to overheating than older, leakier ones. However, the worst-offending buildings for overheating (and there are some shockers) are as often old as they are new. Overheating buildings just tend to be all-round bad buildings: often cold in winter, as well as hot in summer.

It looks as though buildings with too little insulation, too much glazing, not enough shading, and inadequate provision for purge ventilation are at risk of overheating – as are buildings with badly designed and inadequately insulated heating/hot water/community heat systems. Extravagant use of glazing, in particular, seems to have a great deal to answer for.

But there are ways round these dangers, and if designers take all these factors into account, and also use thermal mass carefully (its no good of it sits in the sun all day!)  overheating ought to be less of an issue. However, its important not to skimp on the calculations and modelling during the design process – and equally important not to lose sight of common sense.

Article first published in Green Building, Spring 2014. Apologies for the absence of references – these will be added when I work out the best way to include them.

Overheating: how can we avoid it?

“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… read more

 

 

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.

 

Can Passivhaus teach the policymakers to love the occupant?

Ventilation was much in my mind as I dipped in and out of conversations and seminars at Ecobuild this week. And I began to notice a disturbing tendency for airtightness measures and ventilation to be discussed quite separately, with the costs and benefits of each addressed almost as though the two were unrelated.

Again and again, ventilation appeared to be an afterthought, or a problem, instead of an integral part of the assessment of building performance. Several people also lamented that  “well, you can get draft proofing done on a Green Deal, but ventilation doesn’t meet the golden rule, so who will pay for it? – it can’t be funded”. And alarmingly, this dangerous split seems to be reflected in the very structure of the Green Deal.[1]

This strikes me as rather like saying “you can get this operation that you need, but there is no money to sew you up afterwards”.

Ventilation seemed almost to be resented, an ‘obstacle’ in the way of deeper carbon cuts, limiting what could be achieved. All that fresh air spoils the building performance, it seems.

This put me in mind of a similar flavour you find in discussions about ‘comfort taking’. Once again, the pesky needs of the occupants are getting in the way of the true goal of carbon cutting. Thus in its Green Deal Impact Assessment  DECC complained that “comfort taking” leads to “underachievement in real-world energy savings”.[2] Is it really an “underachievement” to make someone’s house more comfortable?

In both these instances, there is a not-so-hidden subtext that the base animal needs of building occupants are a real hindrance to the low-energy, zero carbon perfection we are seeking. And in a way, you can see how if your job is to achieve these goals, a building with no occupiers would solve a lot of your problems.

So it might be unexpected in a way, that it takes Passivhaus, possibly the most shamelessly geeky and science-based standard of them all, to be the one that not only embraces the occupant, but actually starts from the occupant perspective. My understanding of Passivhaus design is it is built from the premise that occupants want comfortable, healthy buildings that are cheap to run. And yet, somehow, it looks as though Passivhaus manages to deliver the lowest energy and (I think you could easily argue) lowest emissions buildings of the lot of them.

Which is why (or at least one of the reasons why), as I remarked on Twitter this morning, I found that Passivhaus crept into my mind quite often, when I was pondering my uneasiness with what was being said outside the Passivhaus sessions. I think the Passivhaus lot are on to something.



[1]  I was told that for post 1919 buildings there is not anything in the Green Deal that requires the advisors to assess ventilation, even when they recommend draftproofing. There are especially serious concerns about the mass-scale installation of solid wall insulation, where the installer alone is responsible for the ventilation strategy, with no back-stop liability resting with a Green Deal provider. This is an issue that needs more than a blog to tackle – hopefully I will get the chance to come back to this soon.

[2] DECC June 2012 Green Deal Impact Assessment