Multi-storey building retrofit with a focus on the façade selection process: A UK commercial office case study

Poorly-insulated existing buildings contribute significantly to the energy use of the built environment. In the UK, the existing building stock is replaced at a rate of less than 2% a year; thus, many of today’s buildings will still be in use in 2060. Retrofitting aged buildings can significantly reduce their energy use. This paper analyses the selection process and success factors in retrofit façade decision-making. Literature relating to building retrofit and façade selection is reviewed. A case study is conducted on a five-storey 1970s UK commercial office building, retrofitted in 2011. Data is collected via in-depth interviews with key project decision-makers, a documentary evidence review, and thermography of the completed retrofitted façade. The façade evolution is mapped according to seven identified project stages and the RIBA Plan of Work 2007. The retrofit satisfied the client’s aesthetic needs, while delivering an 85% reduction in the 'wall' U-value and a 'B' rated Energy Performance Certificate. Value engineering (VE) greatly influenced the façade selection, with less expensive alternatives replacing original elements of the façade design. The façade’s thermal success is linked to the VE focusing on façade elements covering only a small extent of the building. Façade success factors key to attracting tenants (lower running costs and aesthetics) may apply to commercial buildings in general. Thermography aided in assessing the retrofitted thermal envelope, but to act as a tool to aid retrofit façade selection, it should ideally involve a 'before' and 'after' survey.