[en] When heat waves coincide with loss of access to air conditioning (e.g., due to power outages), the adverse impacts on well-being of occupants will be exacerbated. Hence, there is ongoing interest in using passive strategies to improve the resiliency of buildings under such conditions. One promising strategy is the use of conventional or latent thermal mass to passively mitigate overheating. As a result, Phase Change Materials (PCM), which are already promoted widely as a strategy to use solar energy for passive heating in buildings, may also be a useful strategy to avoid summertime overheating. To verify this, we used whole-building energy simulations to study the effectiveness of PCMs in improving the resiliency of buildings during extreme events. The results suggest a considerable dependence on the timing and duration of power/air conditioning loss episode, the melt temperature of the material, and the underlying climate. We used parametric runs to study the effect of melt temperature on PCM effectiveness to reduce energy consumption while simultaneously increasing the resiliency of buildings during power outages. The results suggest that under some conditions it is possible to optimize melt temperature for both energy efficiency and heat resiliency, while under other conditions, optimizing for one outcome adversely affects the other.

[en] Heat is the number one weather-related killer in the United States and indoor exposure is responsible for a significant portion of the resulting fatalities. Evolving construction practices combined with urban development in harsh climates has led building occupants in many cities to rely on air conditioning (AC) to a degree that their health and well-being are compromised in its absence. The risks are substantial if loss of AC coincides with a hot weather episode (henceforth, a heat disaster). Using simulations, we found that residential buildings in many US cities are highly vulnerable to heat disasters—with more than 50 million citizens living in cities at significant risk. This situation will be exacerbated by intensification of urban heat islands, climate change, and evolving construction practices. It is therefore crucial that future building codes consider thermal resiliency in addition to energy efficiency. (letter)

[en] Highlights: • We demonstrate looking beyond utility cost in assessing building energy efficiency. • Avoided health/climate costs are in the order of magnitude of direct utility savings. • We show that building efficiency can increase the hours comfortable for window use. • Thus reducing the risk of indoor airborne disease transmission per Wells-Riley method. • Efficiency reduces indoor & outdoor (shown via an urban canyon model) heat exposure. Local and state governments find it challenging to adopt aggressive residential building codes that require energy-efficiency upgrades beyond those with a reasonable payback. Thus, economic considerations inhibit the progress towards a more energy-efficient housing stock and often account for direct utility savings. A widely discussed solution is to look beyond energy costs and consider other impacts of energy-saving strategies that affect their financial attractiveness. In this paper, we examine the case of a public housing project in Phoenix, AZ, using several tools to calculate different economic, environmental, and health metrics associated with the three levels of energy efficiency. Our results show that while the payback calculated from direct energy costs may not be attractive, we should consider other savings. We demonstrate that avoided health and climate costs could total around 40% of the direct utility savings. In addition, we quantify how energy-saving strategies can cool the neighborhood, make buildings more resilient to heat, improve indoor air quality, and reduce the transmission of airborne disease. These benefits could be translated to avoid costs in the future.

[en] Highlights: • Indoor & outdoor exposure to extreme heat and air pollution affects human health. • New framework integrates social & health sciences approaches to understanding risk. • Household survey characterizes indoor and outdoor exposure and vulnerability. • Novel application of building energy modeling quantifies indoor exposure. -- Abstract: Urban growth and climate change will exacerbate extreme heat events and air pollution, posing considerable health challenges to urban populations. Although epidemiological studies have shown associations between health outcomes and exposures to ambient air pollution and extreme heat, the degree to which indoor exposures and social and behavioral factors may confound or modify these observed effects remains underexplored. To address this knowledge gap, we explore the linkages between vulnerability science and epidemiological conceptualizations of risk to propose a conceptual and analytical framework for characterizing current and future health risks to air pollution and extreme heat, indoors and outdoors. Our framework offers guidance for research on climatic variability, population vulnerability, the built environment, and health effects by illustrating how health data, spatially resolved ambient data, estimates of indoor conditions, and household-level vulnerability data can be integrated into an epidemiological model. We also describe an approach for characterizing population adaptive capacity and indoor exposure for use in population-based epidemiological models. Our framework and methods represent novel resources for the evaluation of health risks from extreme heat and air pollution, both indoors and outdoors.