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Retrofit Case Studies

Retrofit for the future Nelson Street, Oxford

Figure 1 Retrofit for the future Nelson Street, Oxford (OCC, 2010).

The objective of the works at Nelson Street, along with the other agreed 85 houses that formed the Retrofit for the Future Programme, was to collect data from all around the UK to help the Government and Local Authorities assess how best to reduce the carbon footprint of the social and private housing stocks in the UK by 80% by 2050. Unlike the majority of the projects in the RTFF programme, Nelson Street managed to meet the challenging 80% CO2 reduction targets (OCC, 2010).

The property, an Oxford City Council Victorian semi-detached house in Nelson Street with two rear extensions added in 1972 and 2003, was described as a very cold house by the residents, especially the first floor bathroom that had three exposed external walls and a roof (OCC, 2010).

The project’s objectives were achieved by; raising the property’s standard of insulation to higher energy efficiency levels and minimising heat losses through air leakage by airtight sealing thus reducing the heating load and cutting CO2 emissions by 66%. Adding more efficient water heating and lighting, electrical loads could be further reduced resulting in an overall CO2 emissions reduction of 75%. Adding micro-generation through solar thermal and PV cells installed on the roof further offset energy consumption, achieving a reduction of CO2 emissions by 85% surpassing the target.

The project was design to facilitate innovation and learning, therefore cost effectiveness was not a significant consideration during the project. Overall, the works took 16 weeks to complete, with a two year monitoring programme by Oxford Brookes University undertaken to monitor actual energy consumption (Gupta and Chandiwala, 2010).

Performance/U-valueDetailDate Completed 2010Description76.9m m² Two Bed Mid terraceOwner OccupiedClient/DeveloperOxford city councilSocial rentedConstructionSolid brick wall insulated internally and externally (to rear)Internal solid wall insulation, external solid wall insulation with replacement floor insulationkgCO2/m2/yr.16 kgCO2/m2Based on more lenient SAP modellingPrimary Energy Demand 90kWh/m2/year,Using SAP methodologyAir permeability1m3/m2/hr @50 Pa.Over 10x current building regulationsWallsRear Walls 0.1W/m2K

Front and Gable Walls

0.24W/m2KRear Walls: Internal and external solid wall, cavity wall insulation.

Front and Gable Walls internal and external solid wall insulationRoof 0.1W/m2K420mm loft insulationWindows0.8 W/m2kTriple glazingFloor0.53-0.29 W/m2k

(Proctor, 2015)10mm SpacethermC Aerogel insulation on top of slabHeating SystemNew condensing gas boiler VentilationMVHR –Improve air quality and heat retentionBudget Total refit £118,445£1,540/m2Figure 2 Technical specification Retrofit for the future Nelson Street, Oxford (OCC, 2010)


GUPTA, R. & CHANDIWALA, S. 2010. Understanding occupants: feedback techniques for large-scale low-carbon domestic refurbishments. Building Research & Information, 38, 530-548.

OCC 2010. Oxford Whole House Carbon Reduction Project -Part of the Retrofit for the Future Programme, Sponsored by the Technology Strategy Board. Oxford: Oxford City Council.

PROCTOR 2015. SPACETHERM® C DataSheet. In: LTD, P. G. (ed.).