Greening-the-Box architect Jeremy Harrall explains the low-tech innovations that make 21 The Street so special
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Low-tech retrofit experiment could transform social housing
8th July, 2009
The Greening-the-Box initiative aims to demonstrate that retrofitting can transform hard-to-heat housing association and council properties into models of low-tech sustainability and fuel efficiency - with almost zero heating
From a distance it may look like any other rural council house, but a retrofit experiment taking place in 21 The Street, in the pretty Norfolk village of Ringland, could represent the future of social housing in the UK.
Most of the UK’s 1.7 million council houses were built decades before such things as green building regulations, fuel efficiency and optimised insulation, and in a world of diminishing resources, most are unfit for purpose. Poor design, inefficient use of energy and the rising price of fuel make properties costly for tenants and the environment both – a quarter of the country’s carbon dioxide emissions come from housing sector.
Up until now councils and housing associations have simply been knocking down old stock and building anew, but the question being posed in Ringland is, why demolish when you can retrofit?
Greening-the-Box (GTB) is an initiative introduced by SEArch (Sustainable Ecological Architecture Ltd) and adopted by Wherry Housing Association in partnership with Broadland District Council. Wherry is part of the Circle Anglia group, which manages 46,000 homes across the south of England.
The purpose of the initiative is to transform one of the Wherry’s ‘hard to heat, hard to treat’ 1950s properties – solid-walled and off the gas network – into a blueprint for sustainability its architect hopes to see applied far beyond this little corner of Norfolk.
‘The idea is to see GTB rolled out nationally,’ says SEArch’s Jeremy Harrall, twice winner of the Royal Institution of Chartered Surveyors sustainable building of the year award. ‘We would love to see more housing associations and local authorities take it on, and the British Council has already expressed an interest in implementing the scheme in sub-Saharan Africa.’
GTB’s goals are ambitious – heat-loss reduced tenfold, heating load halved, carbon emissions mitigated by four tonnes a year – but Harrall is confident it will more than answer the sustainable and financial arguments.
The proof of the pudding will be in the living, however. Vacant before the 16-week refit began, the end-of-terrace property is now home to the family of four that had been living next door. They will take part in a three-year monitoring programme covering life-cycle analysis, thermal performance and energy consumption studies.
Though it may not immediately be apparent from the spot-the-difference exterior, their new home will be a radically different animal. All the windows have been double-glazed as a matter of course, but those on the north elevation have been made smaller, reducing the building’s rate of heat-loss. On the south side more and bigger windows have been added to maximise the amount of natural light and transform GTB into a passively, naturally heated building.
Apart from a wood hearth – ‘an open fire warms the human spirit,’ says Harrall – the only other kind of heating is low-grade electric underfloor heating system operated by a switch. No radiators, no gas fires, no oil or mechanical boiler, no flues, no pipes.
As though wrapping up warm, the house’s solid 9in external walls have been clad with an extra 100mm of extruded polystyrene insulation. Factor in the heat contribution from appliances and humans – the average person emits 90w of heat at any one time – and a ground floor of dense concrete, and the superstructure of the building acts like a storage radiator, holding on to its summer heat for the winter months.
‘The trick is to capture and store heat in a healthy way. What we’ve done is upgrade the volume of active or live thermal mass, and as part of the fly-wheel effect, the last net contribution of solar heat from September will start to weep out of superstructure three months later.’
Other features include passive stack and cross ventilation to cool the building, 600mm of quilted recycled plastic insulation in the roof, a rotating cowl on the roof to draw air through the house, breathable walls to reduce condensation, a 1,000-litre rainwater tank, a 300-litre unvented water heater, with water run on to the roof to be heated by the sun, and 800W of photovoltaic panels to be added in the future, subject to funding.
Most of the project’s £100,000 cost was spent on general upgrade work to the house, but GTB’s organisers have itemised the cost of a purely energy-related refit, and calculate it at £36,613 - a much cheaper and less environmentally damaging proposition than the demolition of old stock and the construction of new.
Cost will be a major factor in whether GTB becomes a blueprint for all CircleAnglia’s stock, or a merely an experiment that never came to fruition.
‘Greening the Box is an exciting, innovative and unique pilot project that we hope will help us to improve the lives of our residents, by making them less reliant on fuel,’ says Andy Doylend, executive director of operations at Circle Anglia. ‘Following a thorough and comprehensive assessment of the retrofit and the extent to which heating and water bills are reduced, we will be providing useful data to help the steer the sector as a whole. Once we have the data we will be able to share this with the industry and develop recommendations for replication if it proves to be a long term, financially viable option.’
Claire Astbury of the National Housing Federation hails GTB’s ‘innovative’ focus on low-tech solutions, adding that there is a moral imperative to upgrade poor-performing properties. She says a major rollout of the scheme would need huge funding, however.
‘Social housing rents are controlled by a rent-structuring arrangement,’ she explains. ‘Housing associations can spend money retrofitting properties, but with a reduction in rent due in September, and so a reduction in their income, spending will also be down.’
Other retrofit schemes in the UK seek to circumvent the cost issue by asking tenants themselves to contribute. The Greater Manchester Retrofit Plus initiative, for example, one of the Sustainable Development Commission's 19 'breakthrough' ideas, offers residents and businesses loans for off-the-shelf retrofit packages from approved companies, with the costs repayable over time, perhaps linked to energy savings.
Those achieved by GTB are impressive, with an Energy Efficiency Rating of B/86, an Environmental Impact (carbon dioxide) Rating of A/94, estimated annual carbon dioxide emissions of 0.54 tonnes and annual energy use of 124kWh/m2 (the average UK home emits 7.1 tonnes of carbon dioxide and uses 262kWh/m2 a year). Energy bills are calculated to cost £169.38 a year. The addition of the PV array will reduce costs even further.
Compare this with the house next door: an Energy Efficiency Rating of F/30, an Environmental Impact Rating of F/26, estimated annual carbon dioxide emissions of 7.65 tonnes and annual energy use of 680kWh/m2, and energy bills of £706.63 a year.
Learning how to get the best out of the new home will be the major challenge for its new residents, a culture-shift that will involve their taking charge of this new, greener environment, rather than relying upon technology to manage it. They will be allowed to put rugs down but no carpets, and will be encouraged to leave doors open to allow the free movement of air around the building. The absence of radiators, boilers and thermostats will apparently be the biggest stumbling block.
‘The mindset change is going to be the hardest step for them,’ Harrall anticipates, ‘but the way to do it is through education. The more knowledge they have about how the building works, the principles behind it, the more likely they are to use it to its full potential.
‘What we’ve given them is a green Porsche – or a Tesla – where before they’ve been used to a Ford Anglia. We’ve got to get them driving it to its optimum performance.’
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