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Terraced house refurbishment, Mottingham, London by ECD Architects

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Considered use of products should ensure that ECD Architects’ retrofit of a social-housing property achieves an 80 per cent reduction in carbon emissions.

Refurbishment of existing housing stock is often cited as the panacea to our carbon woes. According to the Energy Saving Trust, the average household can save up to 25 per cent of its annual carbon emissions through energy efficiency, and retrofitting is one way to achieve this.

ECD Architects’ retrofit of a terraced house in Mottingham, south-east London, due to complete later this month, is aiming for a reduction of more than three times that figure, targeting 80 per cent. The project could have a far-reaching impact on how properties owned by Registered Social Landlords (RSLs) are transformed to reduce carbon emissions.

Nondescript terrace
This Hyde Housing Association property is a nondescript brick terraced house built in the 1930s, with a flat-roofed rear extension added in the 1980s. ‘We needed a house that was representative of [Hyde’s] stock,’ says ECD associate director Mark Elton. ‘The idea being that lessons learnt from this project can be rolled out on a larger scale.’

The target od an 80 per cent reduction in carbon emissions was adopted because it is the figure proposed for the UK’s existing housing stock by Brenda Boardman, of the University of Oxford’s Environmental Change Institute, in her Home Truths report. The SAP (Standard Assessment Procedure) rating system, against which the project will be measured, is a scale from 0 (inefficient) to 100 (highly efficient).

‘The fact that it is a brick cavity wall has actually made the job harder than if we’d been given a solid-wall Victorian property [because the former is inherently more energy efficient],’ says Elton. ‘The SAP for the existing building was around 60, and the national average is 48, so getting the 80 per cent reduction has proved quite a challenge.’

PassivHaus standard
The German PassivHaus standard (AJ 28.02.08), which Elton sees as more accurate than the SAP, was used to double-check emissions.
The budget for the project is £80,000 including design fees, but, as Elton points out, this is not a representative figure. Both ECD and main contractor Mears are working at less than cost, and many products are being supplied free of charge or at a discount. A table of predicted costs will be collated and made public at a later date.

On completion, a week of launch events will take place before the house is handed over to the tenant. Parity Projects, a consultancy that works to reduce the environmental impact of existing buildings, will then monitor the performance of the building for two years, periodically publishing the results.

During this period, social housing consultancy (and ECD’s sister company) PPCR will interview the tenant and a control tenant in an existing similar property. ‘It’s a great opportunity for everybody involved to actually put the techniques and materials to
the test,’ says Elton. ‘Hyde is committed to reducing carbon emissions from its stock, and this project will allow it to identify the most cost-effective measures and apply them.’

Start on site date
July 2008
Contract duration 10 weeks
Gross external floor area 98.7m2
Form of contract Exchange of letters only
Cost £80,000, but the true costs based on a roll-out programme will be delivered at the end of the project
Client Hyde Housing Association
Architect ECD Architects
Quantity surveyor/planning supervisor/CDM co-ordinator Keegans
Main contractor Mears  
Annual C02 emissions 9kgCO2/m2 according to SAP

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