Passive and low-energy strategies to improve sleep thermal comfort and energy resiliency during heat waves and cold snaps

Abstract Sleep is a pillar of human health and wellbeing. In high- and middle-income countries, there is a great reliance on heating ventilation and air conditioning systems (HVAC) to control the interior thermal environment in the bedroom. However, these systems are problematic as they are expensive to buy and operate while being energy and environmentally intensive - problems that may increase due to climate change. Passive and low-energy strategies, such as fans and electrical blankets, may address these challenges but their comparative effectiveness for providing comfort in sleep environments has not been studied. We used a thermal manikin to experimentally show that many passive and low-energy strategies are highly effective in supplementing or replacing HVAC systems during sleep. Using passive strategies in combination with low-energy strategies that elevate air movement like ceiling or pedestal fans can enhance the cooling effect by three times compared to only passive options. We applied our experimentally measured heating and cooling effects to two historical case studies: the 2015 Pakistan heat wave and the 2021 Texas power crisis. Passive and low-energy strategies can reduce the sleep time heat or cold exposure by as much as 90%. The low-energy strategies we tested require one to two orders of magnitude less energy than HVAC systems, and the passive strategies require no energy input. Our results demonstrate that these strategies can also help reduce peak load surges in extreme temperature events. This reduces the need for utility loadshedding, which can put individuals at risk of hazardous heat or cold exposure. Our results may serve as a starting point for evidence-based public health guidelines on how individuals can sleep better during heat waves and cold snaps without HVAC.