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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Raymond Pritchard

Narrowing the energy performance gap in non-domestic buildings with aspirational sustainability targets

 

The non-domestic building sector has in recent years witnessed a boom in the number of ostensibly ‘green’ buildings certified under the Building Research Establishment Environmental Assessment Methodology (BREEAM) and similar rating schemes. Despite the proliferation of aspirationally sustainable building designs, the actual energy performance of certified buildings is generally little better and sometimes worse than the building stock average. The actual energy consumption of non- domestic  buildings  is  typically  1.5  to  5  times  greater  than  designer  estimates, resulting in a phenomenon termed the ‘energy performance gap.’

One of the central contributing factors to the energy performance gap is the restricted scope of energy estimate, based around so-called ‘regulated’ loads, so named because of their frequent inclusion in national building regulations. The result of regulation is the near universal exclusion of ‘unregulated’  loads  such as office equipment, plug loads, lifts, catering and IT servers from energy estimates. For an unbiased quantification of the performance gap, it is necessary to develop estimates for these unregulated loads or to exclude such loads from the actual consumption comparison.
Drawing upon data from the University of Cambridge Estate Management, the highly regarded Institute for Manufacturing building was evaluated to further explore the energy performance gap. Assessment of the underlying causes of the performance gap revealed a design-stage optimism bias in the  building development process and lack of prioritisation towards the utility of available energy data. Temporal analysis of sub- metered energy consumption data revealed the usefulness of a simple peak-baseload ratio as a preliminary indicator for building energy performance, with significant energy optimisation potential. Lastly the Estate’s implementation of Soft Landings is critically evaluated against University policy together with the approaches to incentivise energy efficiency across the building portfolio.

Findings from energy-focussed Building Performance Evaluation of the case study building and  associated development context are consolidated to produce recommendations for Estate  anagement.
These recommendations have particular relevance  for  university  estates,  but  are  applicable  also  for  other  non-domestic building portfolios, such as schools and government offices.