A look at the evidence on mechanical ventilation

Natural ventilation often fails – but what is the evidence that mechanical ventilation succeeds? – Investigation for Passive House Plus

There have been a number of studies showing that natural ventilation, dependent as it is on random gaps in the building fabric and the vagaries of wind and weather, is not a reliable source of fresh indoor air. (see here for my article on this)

In theory, mechanical ventilation is under more control, and should work more reliably. But does the evidence bear this out? Does mechanical ventilation deliver good air quality in practice?

I looked into the research to find out whether MVHR, in particular, lived up to the ideal. Continue reading

Electric Heating – time to come in from the cold?

While there are well-established technologies to produce electricity without fossil fuels, decarbonisation of heat is struggling to get under way. Recommended strategies include expansion of low carbon networked heat and possibly the decarbonisation of gas – though these are still only happening at a scale (and with dubious carbon credentials, see PH+ Iss 15 – district heating). However, the commonest proposed means for decarbonising heat is via electrification.

Electrification of heat raises a number of questions about the ability of our power systems to produce enough low carbon electricity and their capacity to transmit it.  But it also represents something of a u-turn in building services design. Continue reading

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

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? – 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

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.