Opinion Operating in the dark
The ‘great British refurb’ will remain a daunting task if we continue to lack building-performance intelligence, argues David Thorpe
L
ast year I was commissioned to write a book on sustainable home renovation that, among other criteria, would help the UK meet its target of reducing global emissions by 80% by 2050. It
seemed reasonable to suppose that there must be plenty of low carbon homes, where it would be possible to see by example what worked and what didn’t. But as I started visiting homes and talking to their occupants, to estate managers and to contractors, it became apparent that this was far from being the case. My research revealed a lamentable shortage of documented, monitored or evaluated refurbishments. In other words, we are largely operating in the
dark. What we do know is that of the environmental renovations that have been evaluated, on average they perform thermally only half as well as predicted, for reasons of poor installation, occupant behaviour or failure of the materials. This year, several monitored projects have begun. Retrofit for the Future is one, government-sponsored, programme tackling this, and several others are being conducted by social housing authorities and academics. Until their results are in, builders and architects have only probabilities as a substitute for evidence. Government thinking is far from clear on what to do
about home renovation, although it does recognise the scale of the problem. It is using carbon cost-effectiveness analysis to provide an estimate of the net social cost per tonne of CO2 reduction resulting from its community- scale energy policies. But I can find no reference to the standards being sought for different insulation measures that are used as the basis for their calculations. Such standards might be: the projected U-value of the home or measure; the air changes per hour; or the absolute final energy use. It’s important to note that these are absolute and not relative criteria; a figure like ‘a 40% reduction’ of CO2 emissions is meaningless if we are unclear of the baseline we’re starting from and the efficacy of the measures. The UK government’s Green Deal proposal, which aims to repay the cost of renovation from the resulting energy savings, lacks such targets. It also carries a high probability of being insufficient to meet the cost of all the necessary modifications. Retrofit for the Future’s
26 CIBSE Journal October 2010
director, Neil Morgan, thinks that to achieve 80% reductions on average will require around £60,000 to £70,000 per property. That is ten times more than the £6,800 figure quoted for the Green Deal. The Passivhaus standard is one, very successful, absolute standard. It provides measurable results; the space heat requirement must not exceed 15kWh/(sq m/a) – less than one-fifth of that mandated by building regulations. Total Primary Energy Use must not exceed 120kWh/(sq m/a) – less than half the average consumption of European new housing. Building fabric U-values must be less than 0.15 W/ sq m K. What if we adopt a standard that approaches this for retrofits? While those homes able to be upgraded to this standard or near it are being dealt with, we could side-by-side have a programme of accelerated replacement of those remaining, with Passivhaus new build. Such buildings eventually pay for themselves with their energy savings – central heating would become a sign not of progress but of obsolescence. We must also beware of apparent solutions, offered by
Of the environmental
renovations that have been evaluated, on average they perform thermally only half as well as predicted
particular manufacturers, that may solve one problem but do not address all of the issues posed by the concept of low-impact housing. The choice of materials is important, too, in overall carbon reduction. The UK’s retrofit challenge is huge. We can achieve a lot with currently available technology, but only if we act with absolute urgency. Meanwhile a lot of research is required and, inevitably, some behaviour change. We also need a massive training programme of designers and contractors, the roll-out of appropriate supply chains and, not least, the sensitisation of Building Control to the issues, so that implementation is scrupulously monitored and improved. l
Sustainable Home Refurbishment: The Earthscan Expert Guide to Retrofitting Homes for Efficiency, by David Thorpe, is published by Earthscan. www.earthscan.
co.uk/?tabid=102285
www.cibsejournal.com
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