District Heating – does it work with Passivhaus?

Cost effective district heating schemes need a nice dense energy demand. They also involve a lot of circulating hot water, which with the best will in the world, is going to involve continuous heat loss. Highly-insulated low energy buildings need very little heat – and in the summer, heat gains can be a positive menace.

So can the two work together? I explored the question a bit in this article for Passive House Plus – downloadable here as a pdf.

District Heating – does it work in Passivhaus?

Risks of Retrofit

A well-designed and well-executed retrofit will not only save energy, it should offer a more comfortable, healthier indoor environment, and protect the building fabric as well. However, there have been a number of warnings about what might go wrong – sometimes, even suggestions that in some instances retrofit measures should not be undertaken at all.

Are these warnings justified? What might go wrong? What is the evidence in practice? In this article, first published in Green Building in 2015, I look at some of the concerns, examine the reasons behind them, and suggest ways to protect building and occupants so retrofit really delivers.

Risks of retrofit – article from Green Building Magazine


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.

Continue reading

Fixing fuel poverty – is there a healthier way?

Fuel poverty causes misery and ill-health – and alleviating fuel poverty by retrofitting homes could potentially offer valuable savings to the health services. However, different approaches to retrofit are likely to have different impacts on health.

The first in this two-part series, published in Green Building in December 2014, looks at how cold, damp homes can harm people’s heath, and at the evidence to date that retrofit can improve matters.  It also explores some pioneering efforts by concerned health organisations to tackle the ill health of their vulnerable patients where it starts – by fixing their cold homes.

The second part, due to be published in Spring 2015, will look a little more closely at different retrofit strategies, and the risks and benefits to occupants – and to the buildings themselves.

PDF download: Fuel poverty and health – Part 1

Continue reading

Prescribing healthy homes

The National Institute for Health and Care Excellence (NICE) recently ran a consultation on the guidance they give to health bodies and local authorities on reducing the burden of winter deaths and illnesses from cold homes.

The AECB (Association for Environment Conscious Building) along with the STBA (Sustainable Traditional Buildings Alliance) and Severn Wye Energy Agency submitted a  response, which I helped to draft.

The response welcomed the idea that health professionals should be involved in identifying and tackling unhealthy homes. It also emphasised that excess winter deaths and illnesses were almost certainly due to a combination of low indoor temperatures and poor indoor air quality (exacerbated by cold surfaces in uninsulated homes, and by occupants restricting ventilation to keep out cold draughts), and that an emphasis on low temperatures alone could miss significant causes of ill-health – and valuable remedies.

You can download the response here: NICE excess winter deaths and illnesses consultation response

You can also find out more about the original NICE consultation on the AECB website here


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



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