Indoor Temperature and Air Conditioning Use in Phoenix, AZ: A Household Study

Heat-related discomfort, injuries, and deaths often occur due to indoor heat exposure in the developed world. However, our understanding of determinants of indoor thermal conditions is severely limited by a paucity of data. Previous studies concerning indoor environments have generally focused on the physical factors (e.g. outdoor temperature, incoming solar radiation, prevailing surroundings, and building variables) that control indoor temperature, with less attention to social and behavioral factors (e.g. access to cooling resources and the extent of their usage, resource constraints, thermal preference, and demographic variables). These social and behavioral factors likely account for a significant portion of the variance in indoor conditions within and between households.

The 3HEAT Project is an NSF-supported interdisciplinary collaboration between researchers at Arizona State University, Georgia Tech, and University of Michigan investigating the specific social and environmental mechanisms that determine urban vulnerability when independent or coupled heat and power failure events occur. To address the gap in connections between social and behavioral factors and residential indoor thermal environments, we present findings from research conducted in the summer of 2016 as part of the 3HEAT Project. We administered surveys to 163 Phoenix residents and continuously monitored indoor temperature and humidity in a subset of 46 of these households for six weeks. In the survey, residents were asked about their experiences and perceptions of heat waves, including their use and access to indoor temperature modifying behaviors. Utilizing a two-stage clustering approach incorporating hourly mean, variance, and diurnal range of indoor temperature and humidity in each of the 46 households, specific quantitative cooling profiles were revealed and matched with survey responses indicating degree of constraint on resources (such as air conditioning), risk perception, and demographic variables. Addressing indoor heat exposure requires characterizing the indoor thermal environment in a way that can be effectively communicated to decision-makers and stakeholders. By identifying shared social and behavioral characteristics among households within each cluster, and particularly in houses with higher temperatures, we can identify populations that are more at risk and design and tailor appropriate intervention measures.