First evidence for the reliability of building co-heating tests

Abstract

This paper provides powerful evidence empirically demonstrating for the first time the reliability of the co-heating test. The test is widely used throughout Europe to measure the total heat transfer through the fabric of buildings and to calculate the heat-transfer coefficient (HTC; units W/K). A reliable test is essential to address the ‘performance gap’, where in-use energy performance is consistently, and often substantially, poorer than predicted. The co-heating test could meet this need, but its reliability requires confirmation. Seven teams independently conducted co-heating tests on the same detached house near Watford, UK. Despite differences in the weather and in the experimental and analytical approaches, the teams’ final reported HTC measurements were within ±10% of the mean. With further standardization it is likely to be possible to improve upon this reproducibility. Furthermore, uncertainty analysis based upon a 95% confidence interval resulted in an estimated uncertainty in HTC measurements of ±8%. This research addresses persistent doubts about the reliability of the co-heating test. Avenues to further improvement of the test are discussed. This work helps to enable the test’s wider adoption as a component of the regulatory process and thus improvements to standards of house construction.