Building characteristics as determinants of propensity to high indoor summer temperatures in London dwellings

Cities are expected to experience an increasing risk of overheating due to the combined effects of climate change and the urban heat island phenomenon. Although external factors, such as urban morphology and greening, may influence the spatio-temporal variation of overheating risk, the characteristics of individual buildings are also likely to be important. This paper presents the results of simulations of indoor temperatures for 3,456 combinations of dwellings types and characteristics selected to represent the domestic stock in Greater London, UK. The simulations were carried out using the EnergyPlus dynamic thermal modelling software with external weather conditions represented by the CIBSE Design Summer Year weather file. Simulation results were analysed to assess the relative effect of dwelling characteristics on both mean and maximum daytime (8 am to 11 pm) living room temperatures during the warmest continuous 5-day period of modelling. The simulations suggested appreciable variation between dwelling types but generally greater variation within dwelling type depending on such factors as orientation, surrounding buildings and levels of (retrofitted) insulation. Dwellings with comparatively high daytime mean and maximum living room temperatures included selected dwellings within three- or four-storey line built walk up flats and purpose-built mews, built 1914-1959, and bungalows and single storey houses, built 1914-1945. Retrofitting of insulation measures had considerable impact on indoor temperatures, with combined retrofitting of roof insulation and window upgrades reducing daytime living room temperatures by, on average, 0.76 (%95 C.I. 0.63, 0.89) °C for mean temperature and 1.30 (%95 C.I. 1.05, 1.54) °C for maximum temperature. On the other hand, retrofitted wall and, to lesser degree, floor insulation tended to increase daytime living room temperatures, with a combined effect of 0.46 (%95 C.I. 0.33, 0.60) °C increase in mean temperature and 0.71 (%95 C.I. 0.47, 0.96) °C increase in maximum temperature. For some dwellings, insulation measures decreased maximum temperatures by up to 6 °C, while in others it increased maximum temperatures by over 2 °C. These results suggest that the specific (limited) insulation measures can result in appreciable modification of overheating risk in the particular modeled dwelling types. Within the context of a changing climate, knowledge of insulation characteristics after retrofitting is crucial for the accurate identification of dwellings with greatest overheating potential.

Building characteristics as determinants of propensity to high indoor summer temperatures in London dwellings. Building and Environment, 55 117-130. 

Mavrogianni, A., Wilkinson, P., Davies, M., Biddulph, P., Oikonomou, E. (2012)