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Building Performance Evaluation Programme: Findings from non-domestic report

This summary outlines the challenges that may be faced in order to achieve a reduction of 80% in greenhouse gas emissions by 2050 in non-domestic projects and presents measures to overcome them. The study looks at 50 leading edge buildings including schools, offices, supermarkets and healthcare facilities. It examines the buildings’ fabric and systems and occupant satisfaction with the building.

Key Findings

  • Average total carbon emissions were 3.8 times higher than the average design estimate – and only 1 of the 49 buildings had actual carbon emissions that matched the design estimate.
  • The range of energy use per square metre across the projects was very wide – from 28 to 367 kWh/m2 for electricity, and from 0 to 316 kWh/m2 for fuel. The average electricity use across the buildings was 103 kWh/m2, while the mean for fuel was 92 kWh/m2.
  • Energy Performance Certificates (EPCs) do not reliably predict actual energy in use in buildings.
  • The average tested air tightness across non-domestic buildings was 6.1 m3/m2.h – significantly better than the minimum requirement in Building Regulations.

Further Detail

There was no single recipe which created a successful building with low energy use and carbon emissions. Designers and developers tend to install overly complex control systems, prompted partly by building regulations and BREEAM credits. Users not understanding these systems means energy is wasted and/or overheating.

Natural ventilation proved to be a key element in buildings with low-carbon emissions, whereas buildings with high emissions were often associated with poor control of space and water heating and/or lighting. Innovate also highlight how important it is to have fine, and ideally manual, controls which was found applicable for natural ventilation systems as “…finding the balance is a nightmare”.

An occupant satisfaction survey was carried out using the Building Use Studies (BUS) methodology to evaluate post-occupancy satisfaction. The occupant satisfaction survey revealed temperature and air quality in summer were the leading causes of poor satisfaction with 31% and 28% unsatisfied.Temperature in winter was a concern with 20% unsatisfied, while 19% said perceived health, 17% said air quality in winter and productivity was also poorly rated by 17%.

More than three quarters of the buildings scored above average for image to visitors (83%), lighting (80%) and comfort (76%), indicating that most of the projects are designing buildings that promote a positive image and offer good daylight, electric lighting and provide comfortable facilities.

To read this report in full, click here.

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