Architecture -
Retrofit and
Sustainable Development

TSB Nelson Street

Ridge has recently completed the Retrofit of a social housing unit as part of The Technology Strategy Board’s ‘Retrofit for the Future’ campaign. The pilot study has revealed many lessons in building fabric improvements and use of renewables, such as PV panels for reducing the energy demand of social housing.

The scheme has been delivered in two phases: Phase 1, the feasibility and design phase, enabling projects to work with suppliers to devise solutions to make cuts in carbon emissions produced by social housing; and Phase 2, the build phase.

As part of the initial design phase, Ridge was one of the organisations to be awarded Government funding, through the Technology Strategy Board, to carry out full feasibility studies and devise innovative proposals. The work looks at the building envelope and services installations and considers the cost per tonne of CO2 saved, exploring the options available to apply to existing low rise housing to meet the Government’s target to reduce CO2 emissions by 80% by 2050.

Ridge has worked with Oxford City Council and Oxford Brookes University to develop cost effective solutions that can be rolled out on a mass scale across the affordable housing stock.

We have completed four feasibility studies on domestic properties to investigate cost effective methods of reducing carbon emissions from existing housing by 80% from the 1990 base level to 17kg/m²/year and a primary energy demand of 115kwh/m²/year.

The challenge was to consider how best to achieve methods that delivered the most cost effective solutions in terms of £/tonne of CO2 saved and develop solutions that could be repeated on a mass scale to address the energy consumption of the 4.1million affordable homes across the country.

Ridge met this challenge by adopting a whole dwelling solution that sought to reduce the energy demand first and then consider the most appropriate form of meeting the reduced demand including traditional as well as renewable technologies.

To assess the most effective solution, each solution was considered one by one and then blended to deliver the most appropriate solution.

To better understand the performance of the buildings, working with Oxford Brookes University, Ridge undertook a number of surveys including a physical survey, interviewing the residents, consulting other stakeholders, thermal imaging of the dwellings, air pressure testing to establish air leakage rates, air quality monitoring (including temperature, humidity and CO2), review of energy bills for the properties over the past 12 months and SAP assessments of the existing structure. This data provided invaluable information on how the existing dwellings performed and we were able to measure actual energy use against predicted energy use on the base building.

Using an extended SAP 2005 model developed by the BRE, we were able to assess each of the proposed solutions and calculate the proposed SAP rating and reduction in energy use. The extended SAP model accounted for portable lights and appliances whereas normal SAP does not. We then prepared budget costs for each solution to be able to assess the cost effectiveness of each solution in terms of £/tonne of CO2 saved. The cost model used a 60 year life and allowed for replacement of services components on a 15 year life cycle.

Our approach was to address the building fabric first to provide additional levels of insulation to much higher levels than current building regulations. This included the roof, external walls, windows and doors and the ground floor. Air leakage was reduced and cold bridging was addressed by carefully considering details such as window reveals, chimneys and junctions of floors with external walls. The CO2 emissions and primary energy demand could be reduced by up to 60% by enhancing the insulation levels alone before considering services alterations. With the reduced energy demand the most appropriate forms of servicing this demand were considered including using traditional gas fired boilers, ground and air source heat pumps, solar water heating and PV arrays. To meet both targets, a mix of solutions was arrived at.

Ridge, working in partnership with Oxford City Council and Oxford Brookes University, is embarking on a two-year monitoring project to fully realise the performance of each of the innovations on the house.