[Feature + five case studies] Architects are at the forefront of a retrofit movement that is both low-carbon and high-tech, writes Martin Spring
More from: Retrofit for the Future
Scattered all around the UK, 119 houses have been radically refurbished with one specific aim. They are all designed and built to comply with the government’s legal commitment to slash all CO2 emissions by 80 per cent by the year 2050.
Called Retrofit for the Future, this refurbishment programme is the first official attempt ‘to demonstrate if and how 80 per cent and more of emissions can be achieved in existing housing stock’.
It has been given £17 million in funding by the government-backed Technology Strategy Board (TSB).
The 119 retrofits are managed as 86 self-contained projects, each on its own site and a few including more than one dwelling.
All but nine of the winning teams include architects, such as PRP Architects, ECD Architects and ZEDfactory, who are working alongside energy consultants, services engineers and contractors.
Only dwellings in public ownership are included in the programme. As well as archetypal 1960s council houses, they encompass a broad range of built forms and construction types from 19th-century brick terrace houses to inter-war semi-detacheds, and even the odd system-built concrete dwelling.
The retrofit programme is overseen by Ian Meikle, head of TSB’s Low Impact Building group, and architect-turned-energy-performance expert Paul Ruyssevelt.
Innovation is one of the stated aims of the programme, and Meikle is proud of innovations that address the particular problems of retrofit as distinct from new build.
‘I suspect that none are absolutely innovative, but it often takes 25 or 30 years for new materials to reduce in cost and permeate the British building industry,’ he says.
He singles out a product called Wattbox, which he calls ‘the latest smart control unit for self-learning’. By monitoring the energy consumption of all appliances in the house, it enables the occupants to make savings by controlling their usage.
Another new material is high-performance aerogel insulation. ‘In an existing bathroom 1.8m long, you have a problem of drylining it in thick insulation and fitting in sanitary appliances,’ says PRP Architects’ environmental director, Andrew Mellor.
‘So on our house on Follett Street in east London, we used Cabot Nanogel, which is an aerogel product originally developed by NASA to insulate spacecraft. We applied it in six layers, each 10mm thick, and finished it off with 9mm plasterboard.’ The total U-value for the drylined wall is 0.23 W/m2K.
Also new to the British market is a highly insulated double-glazed window filled with an inert gas such as Xenon and Krypton. PRP specified inert-gas windows manufactured in Japan for the Follett Street retrofit, which lies within a conservation area.
With the cavity between panes no more than 4mm wide, double-glazed units could be housed in traditional sliding timber sashes that, when viewed from the street, exactly match the single-glazed originals they replaced.
Some widely applicable innovations have been devised by architects themselves. For Prewett Bizley Architects, applying external insulation and render 285mm thick posed a problem when applying the roof gutter.
But instead of stripping the roof covering to extend the rafters, Rob Prewett designed a special gutter wide enough to cover the insulation.
ZEDfactory has tackled the problem of retrofitting a house while it was occupied. To avoid pulling up floorboards to fit insulation, the practice specified polystyrene beading, normally used in cavity insulation, which was blown into the floor void.
However, this solution posed another abiding risk of boosting insulation in existing buildings: interstitial condensation. So ZEDfactory specified moisture meters to be fitted on the vulnerable joist ends.
An essential part of the Retrofit for the Future programme is to monitor energy use and CO2 emissions from the occupied houses over two years.
Designs and energy/CO2 predictions are already publicly accessible on www.innovateuk.org/retrofit, but full results will not become meaningful until the end of the first heating season in a year’s time.
Yet even with occupation by genuine lay families, the 86 projects are nothing more than experimental prototypes.
The far vaster problem is how to roll out retrofit to the same standard across the 21 million existing dwellings that the Technology Strategy Board reckons will still be occupied in 2050. Two further projects currently underway are investigating how retrofit can be geared up to a national scale.
One managed by the Energy Technologies Institute covers the UK and includes PRP Architects as one of eight contributors. The other covering all of Europe is called Eracobuild.
The first sticking point is cost, and Retrofit offers no solution, as its experimental projects each come at the inflated price of £142,000. But Ruyssevelt believes that a three-bed semi-detached can currently be retrofitted to achieve 80 per cent CO2 reduction for £25,000 to £30,000.
As retrofit is rolled out, economies of scale will come into play. New materials and components that are currently classed as specials will be geared up into standard production. As well as speeding up material supplies, this should reduce total build costs by 20 to 40 per cent, he argues.
Meikle puts his faith into new technology-assisted site processes to speed up construction on site. The contractor, United House, is already using a 3D laser system that simultaneously measures the dimensions of all surfaces within a room with an accuracy of 3mm.
‘Lining panels can be accurately cut off-site by machines to minimise wastage’ says Meikle. ‘This means that 10 properties can be fitted out in the time that it currently takes to do one.’
As for the architect’s role in retrofitting, Meikle believes they hold the key to what he calls ‘the new professionalism’ that transcends the traditional ‘man-and-van’ approach.
By this he means applying a ‘repeatable’ approach that is different from a standard package, in that it can be adjusted to suit the myriad of existing houses, each one individual and in some way different from the rest.