Tackling hard-to-treat Homes in South Bristol

Investigating innovative ways to reduce carbon emissions from solid-walled houses in South Bristol

Project duration: April 2003 to April 2004

The aim of this project was to investigate innovative ways of reducing domestic carbon emissions from solid-wall Victorian properties in south Bristol. The project examined the issues associated with cutting carbon emissions in hard-to-treat homes and their implications for both Bristol City Council and UK Government policies to improve energy efficiency and tackle fuel poverty and climate change.

This project built on the knowledge and skills gained in the Sanford Carbon 60 study. That study showed that, through a combination of energy efficiency measures, carbon emissions at a London housing cooperative could be cut by nearly 30%. The addition of gas condensing boilers increased the figure to 45%, while a combined package of energy efficiency, renewables and behavioural changes achieved cuts of 70%. By adding green electricity to the combined package, the figure rose to 100%.

In contrast, the solid-wall construction of the south Bristol properties means that applying the same set of measures would bring about lower carbon reductions, making this project very different and challenging.

CSE developed three scenarios that correspond to established Government targets for reducing emissions: low (20% — the Government target for 2010); medium (40% — an intermediate target set for this project); and high (60% — the Government target for 2050). A 20% cut is considered ‘achievable’, 40% ‘difficult’ and a 60% reduction required radical changes and the application of innovative measures.

CSE adopted an innovative, holistic approach, including an energy awareness programme for residents, improving the thermal efficiency of the properties through insulation measures, reducing fuel consumption through the use of more efficient appliances, introducing embedded renewable and low-carbon energy generation, and reducing emissions associated with resident transport.

The properties were assessed using NHER software to rate their thermal efficiency and assess current levels of carbon emissions. This was compared with actual consumption data based on residents’ fuel bills. Residents completed questionnaires designed to collect data which was used to calculate household ecological footprints, with software provided by Best Foot Forward in order to understand how behavioural change could reduce household carbon emissions. Options for improving the thermal efficiency of the dwellings and household-scale combined heat and power generation were also appraised.

The project concluded in 2004. The results of the feasibility study suggest that, by installing energy efficiency measures, carbon emissions for SCHA as a whole can be cut by 23%. The addition of gas condensing boilers improves this to a 34% reduction. If renewable energy technologies are introduced, carbon reduction would be 46% if using photovoltaics and 64% if biomass boilers and a ground source heat pump are used instead of gas condensing boilers. By using these two renewable technologies together, a 75% reduction is possible, increasing to 95% if all the properties switch to a green electricity tariff.

The report concluded that the most practicable option is to build the reduction targets into an action plan staggered towards 2050, e.g. 20% by 2010 (minimum), 40% by 2020 and 60% by 2050. The report is due to be published early in 2005 and will be available on CSE's website.

For further information contact:

Simon Roberts OBE | 0117 934 1441


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