Heat loss through the building fabric: Low carbon construction practice

For domestic buildings to meet current definitions of zero carbon the building fabric and services must achieve 70% reduction in energy use, taking the carbon emissions down to less than 7 Kg CO2/m2. However, there is a significant obstacle to such endeavours. The limited information on the thermal performance of buildings means that the designs are theoretical. Very few models have been tested against the as-built product and where tests have taken place the cyclical process of research and development is taking time to feed back into the design and construction processes. The gaps in our knowledge of building physics are considerable, designs are not robust and buildings are falling short of their expectations. An intensive study of 18 houses was undertaken to examine the design and onsite assembly, comparisons were made between the predicted energy performance and that achieved once the design was built. The heat losses were, on average over 40% worse than predicted. The forensic analysis of the design and construction process revealed that buildings do not perform as designed due to missing or incomplete information, incorrect detailing, ad-hoc adjustments on site, incorrect assembly of materials, poor workmanship and failure to commission buildings and their services properly. From the research, a list of problems has been produced with the aim of avoiding such defects in the future.