Conference Agenda

Energy efficiency certification is a central instrument of climate and housing policy. This study provides the first evidence on whether, and to what extent, ambient temperature at the time of inspection distorts the assessors’ energy performance certificate (EPC) scoring decisions. Using a dataset of over 18.5 million EPCs from England and Wales (2008–2025) linked with high-frequency weather and pollution data, we uncover a strong non-linear and asymmetric relationship between temperature and EPC scores: extreme cold significantly inflates scores, while heat generates smaller but systematic downward adjustments. On days below −5 °C, scores rise by about 1.6 points, which is large enough to push many properties across EPC rating thresholds. We identify behavioural mechanisms related to assessor effort and cognitive performance. Cold conditions reduce assessors’ effort in conducting detailed on-site checks, resulting in upward-biased efficiency scores, whereas heat impairs attention and judgment, leading to stricter evaluation. A back-of-the-envelope calculation suggests that temperature-induced upgrades near lower rating thresholds can raise house prices by £5,220–7,250 using the annual average UK dwelling price of 2024. Our findings reveal a previously overlooked channel through which climate-related temperature variation undermines the reliability of environmental policy and the efficiency of housing markets.