Can Solar Shade Structures Significantly Reduce Interior Automobile Temperatures?

Each year, hundreds of children and pets are left inside vehicles parked in the sun. Nowhere is that more dangerous than in the southwest where skies are clear nearly 300 days a year. Not only can air temperatures inside the vehicles reach 54C within an hour, surface temperatures like steering wheels and dash boards can reach 88C in that same hour – the time it takes for a trip to the grocery store. Most shopping centers do not have covered parking, but if they did, their customers could enjoy much cooler vehicles and the potential for loss of a child or a pet would be reduced. In Phoenix, shaded parking places are coveted, but how much does shade lower interior vehicle temperatures? We tested the cooling effects of solar shade structures under clear summer conditions. Three matched pairs of vehicles (sedan, van, economy) were parked one in the sun and one under the shade structure to simulate one-hour shopping trips. Before and after each “trip”, interior surface and air temperatures were recorded, with continuous recording of air temperature. After each trip, the AC was run to drop the air temperature back down to 29C. Vehicles in the sun had an average interior air temperature of 47C, and 39C for the shaded vehicles. Dashboard temperatures averaged 72C and 51C in the sun and shade, respectively. Steering wheel temperatures averaged 57C and 43C in the sun and shade, respectively. The heating rate in the sun averaged 0.41C/min and 0.25C/min in the shade. Economy cars heated the fastest, while vans heated the slowest, likely due to air volume. Sedans cooled the fastest while vans cooled the slowest. Average hourly air temperature increase was 23C in the sun and 13C in the shade. T-tests confirmed that shade significantly lowers interior car temperatures. Shading parking lots, either though natural or artificial structures, not only provide safety benefits by reducing the potential for heat stroke deaths to children and pets, but also reduces the risk of burns from hot surfaces, as well as reducing the time and energy required to cool vehicle interiors to ambient outdoor temperature.