A health risk matrix for assessing the impacts of heat and cold exposure in residential buildings

• BACKGROUND AND AIM With people in developed countries spending 70% of their time at home, the impact of the built environment on human health is vital. Although there has been ample epidemiological evidence on the relationship between high/low outdoor temperature exposures and adverse health impacts, there is a paucity of research investigating how residential characteristics and human behaviours might affect temperature-related health risks. This research aims to fill this gap. • METHODS A health risk matrix was obtained by applying a four-stage spatiotemporal health risk assessment framework (comprising hazard identification, exposure assessment, exposure-response assessment and risk characterization) to estimate the temperature-cardiovascular mortality relationship in Greater Taipei, Taiwan, using paired observations of outdoor-indoor temperatures and PM2.5 concentrations in dwellings. • RESULTS Residential characteristics and household energy use acted as moderators, and indoor temperature functioned as a mediator in the temperature-mortality relationship. A three-dimensional matrix projected outdoor temperature, human vulnerability and dwelling type along three axes to visualise the cardiovascular mortality risk. Human vulnerability represents the interaction between outdoor temperature and household energy use. By multiplying the risk levels (1-3) of each of the three axes, a total of 27 levels of health risk are obtained. • CONCLUSIONS This study encourages carefully-planned climate change mitigations and adaptations to achieve healthier indoor environments: (1) Strategies for reducing temperature-related cardiovascular mortality should incorporate the energy use for heating/cooling, which may affect human vulnerability and be affected by the household income, prevalence of air conditioning systems, green area, and population rate of older people. (2) Building retrofits for improving energy efficiency should carefully consider dwelling thermal types, which may vary with occupants’ behaviours and cause unintended health consequences when indoor temperature closely follows outdoor temperature and makes dwellings overheat or excessively cold. • KEYWORDS Health risk assessment, Health matrix, Temperature-related mortality, Dwellings, Human behaviours