Tent Shades: Heat Relief or Added Strain for People Experiencing Homelessness?

Homelessness and heat hazards persist as public health concerns in many cities globally. The concurrence of these two urban challenges exacerbates vulnerability. Responses from local authorities and modified personal behavior are often implemented to enhance resilience. One observed strategy to prevent exposure to direct sunlight is using tent shades. We tested the efficiency of four commonly used tent shades by people experiencing homelessness in the Phoenix area over identical tents (tarp, mylar, white bedsheet, and aluminum foil). We compared them to ambient conditions and a control tent. We monitored meteorological variables at all six locations, notably air temperature (T_air) and the Mean Radiant Temperature (MRT). We applied statistical techniques and physiological modeling to determine the heat experiences of people experiencing homelessness under the sweltering summer conditions for the various shade types. The results show that using tent shading led to a notable reduction in in-tent MRT during daytime hours (p<0.05). However, the shades amplified the risk of in-tent thermal discomfort at night when compared to both the control tent and the immediate ambient conditions. In addition, the choice of temperature metric matters, and using only either MRT or T_air to assess heat experiences in the tents could lead to inconsistent conclusions about in-tent microclimate. We found evidence of higher risk heat strain, with core temperature exceeding 40˚C for users of drugs. We recommend testing the effectiveness of heat-intervening strategies to prevent heat-related illnesses and mortality. Our study does not support the use of tents or shade covers as a viable strategy for heat relief, especially for populations at the highest risk of heat such as people experiencing homelessness.