Multi-scale analysis of exposure to heat in Southeast England

Outdoor temperatures experienced by people in urban areas are typically higher than those in rural areas due to the urban heat island, but indoor temperatures also vary as a result of differences between buildings. We combined modelling of temperature at city and building scales, to determine the most important sources of variation in exposure to heat stress across London and Southeast England. 

We modelled outdoor temperatures using the WRF model with BEP-BEM for the hot summer of 2018, and used the output to force the EnergyPlus building model to estimate indoor temperatures of residential buildings.

We investigated variations in the residential building stock across the region, as well as demographics. The latter is important because health risks posed by heat also vary with the population’s age, health, and socioeconomic status.

Within the study region, we found large differences in exposure to heat between the urban population of London and the general population of Southeast England, and that as a result outdoor heat exposure is highest for ethnic minority groups, younger people, and the more socioeconomically deprived. However, variations in outdoor temperature within the urban areas of London were much smaller than the variations between London and the rest of the southeast.

We compared the variation in the outdoor temperature with the variation in indoor temperature, building on evidence that flats (apartments) are more likely to overheat, and are more often located in hotter parts of the city than houses. This has implications for interventions on the built environment designed to reduce the health impacts of heat.

By combining thermal modelling at different scales with demographic data, we aim to improve understanding of the sources of personal variations in heat-hazard within the population.