Comparing temperature-related mortality impacts of cool roofs in winter and summer in a highly urbanized European region for present and future climate

Helen L Macintyre,Clare Heaviside,Xiaoming Cai,Revati Phalkey

doi:10.1016/j.envint.2021.106606

Helen L Macintyre, Clare Heaviside + Show 2 more

Open Access

https://doi.org/10.1016/j.envint.2021.106606

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Abstract

Human health can be negatively impacted by hot or cold weather, which often exacerbates respiratory or cardiovascular conditions and increases the risk of mortality. Urban populations are at particular increased risk of effects from heat due to the Urban Heat Island (UHI) effect (higher urban temperatures compared with rural ones). This has led to extensive investigation of the summertime UHI, its impacts on health, and also the consideration of interventions such as reflective ‘cool’ roofs to help reduce summertime overheating effects. However, interventions aimed at limiting summer heat are rarely evaluated for their effects in wintertime, and thus their overall annual net impact on temperature-related health effects are poorly understood.In this study we use a regional weather model to simulate the winter 2009/10 period for an urbanized region of the UK (Birmingham and the West Midlands), and use a health impact assessment to estimate the impact of reflective ‘cool’ roofs (an intervention usually aimed at reducing the UHI in summer) on cold-related mortality in winter. Cool roofs have been shown to be effective at reducing maximum temperatures during summertime. In contrast to the summer, we find that cool roofs have a minimal effect on ambient air temperatures in winter. Although the UHI in summertime can increase heat-related mortality, the wintertime UHI can have benefits to health, through avoided cold-related mortality. Our results highlight the potential annual net health benefits of implementing cool roofs to reduce temperature-related mortality in summer, without reducing the protective UHI effect in winter.Further, we suggest that benefits of cool roofs may increase in future, with a doubling of the number of heat-related deaths avoided by the 2080s (RCP8.5) compared to summer 2006, and with insignificant changes in the impact of cool-roofs on cold-related mortality. These results further support reflective ‘cool’ roof implementation strategies as effective interventions to protect health, both today and in future.

Highlights

Hot or cold weather can negatively impact human health, potentially exacerbating conditions such as respiratory or cardiovascular diseases, and leading to increased risk of hospitalization and death (Basu, 2009; Gomez-Acebo et al, 2013; Guo et al, 2014)
The Urban Heat Island effect (UHI) has been shown to contribute to negative heat-health outcomes (Heaviside et al, 2017), with the summer UHI associated with increases in heat-related mortality, and effects in winter being less clear, though studies suggest a protective effect on cold-related mortality; for the West Midlands, a heavily urbanised area of the UK, it has been shown that ~40% of heat-related mortality could be attributed to the UHI intensity during summer 2006, and up to 50% during the heatwave of 2003, with increasing impacts on heat-related mortality in future (Macintyre and Heaviside, 2019; Heaviside et al, 2016)
Cool roofs have a negligible effect on cold-related mortality (4 additional cold-related deaths; 0.23% of overall cold-related deaths) in winter, which corresponds to 1% of those avoided due to the UHI (Fig. 3a)

Summary

Introduction

Hot or cold weather can negatively impact human health, potentially exacerbating conditions such as respiratory or cardiovascular diseases, and leading to increased risk of hospitalization and death (Basu, 2009; Gomez-Acebo et al, 2013; Guo et al, 2014). The UHI has been shown to contribute to negative heat-health outcomes (Heaviside et al, 2017), with the summer UHI associated with increases in heat-related mortality, and effects in winter being less clear, though studies suggest a protective effect on cold-related mortality; for the West Midlands, a heavily urbanised area of the UK, it has been shown that ~40% of heat-related mortality could be attributed to the UHI intensity during summer 2006, and up to 50% during the heatwave of 2003, with increasing impacts on heat-related mortality in future (Macintyre and Heaviside, 2019; Heaviside et al, 2016). The winter UHI has received far less attention than the summer UHI, but has been shown to poten tially protect against up to 15% of cold-related mortality in a cold winter (UK, 2009–2010), with the future impacts showing little change (Mac intyre et al, 2021)

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