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On air

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BRE takes a cool look at air conditioning in non-domestic buildings.

A newly published BRE report sheds important light on electricity usage by air conditioning in UK offices and retail environments. Comprising the findings of a two-year study commissioned by the Department of Energy and Climate Change (DECC) – now part of the Department of Business, Energy and Industrial Strategy – the report provides key insights into how the energy is being used and the factors influencing consumption.

The aim of the study was to improve the DECC’s understanding of UK electricity usage by air-conditioning (AC) in UK non-domestic buildings. Led by Dr Andy Lewry, BRE’s principal consultant, in the sustainable energy team, the study included analysing existing cooling demand and consumption data; assessing air conditioning inspection reports and energy performance certificates; reviewing literature on trends in air conditioning usage and the possible future impacts of new technology; and developing procedures to extend the scope of DECC’s product policy model.

With the research informing objectives ranging from estimating the potential for energy efficiency to how uptake of energy-efficient appliances can be accelerated, the main findings and outcomes include:

  •  Cooling in air conditioning systems may account for around a tenth of total UK electricity consumption.
  • Heat-waves are becoming more frequent across the UK and in the South-East of England, the number of heat-wave days per year increased from 5 in 1961 to 17 in 2003.
  • The proportion of buildings with air-conditioning is increasing. The study estimates that that, in 2012, some 65% of UK office space and 30% of UK retail space was air-conditioned.
  • The study estimates that cooling in offices typically uses around 40 kWh/m2 per year.
  • Air conditioning is frequently used even when buildings are unoccupied, for example in the evenings and over the weekends.
  • The analysis of Energy Performance Certificates (EPCs) indicates that over half of air conditioning systems in the UK are split systems. Although only 10% of EPCs have AC recommendations; these mostly relate to more efficient equipment, including variable speed drives, and reducing air leakage from ductwork
  • An analysis of the recommendations in air conditioning inspection reports, which tend to be generic with the focus on improving controls and maintenance.
  • Recommendations for updating the key inputs into DECC’s existing product policy model of air conditioning electricity demand and development of an algorithm to estimate peak and monthly demand to supplement it.

BRE has also put together a dissemination plan aimed specifically at air-conditioning designers and technicians, building managers and smart system designers

The full report with appendices is freely available on BRE’s website at


For further information please contact Linda McKeown, BRE, email [email protected]


The views expressed in this report are those of the authors – Alan Abela, Lorna Hamilton, Roger Hitchin, Andy Lewry and Christine Pout, and not necessarily those of the Department of Energy and Climate Change (nor do they reflect Government policy). It is published under the conditions of the Open Government Licence; i.e., this information (not including logos) may be used free of charge in any format or medium, subject to the terms of this Licence. To view this licence, visit or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: [email protected]. Any enquiries regarding this publication should be sent to Penny Dunbabin (email [email protected])

BRE has used all reasonable skill and care in respect of this report but does not warrant its accuracy or completeness. BRE does not guarantee that this report will be free from errors and omissions.


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