On the impact of innovative materials on outdoor thermal comfort of pedestrians in historical urban canyons

Urban heat island is an anthropogenic phenomenon affecting urban outdoor thermal comfort conditions and energy utilization. This is even truer in urban canyon configurations, characterized by low sky view factor and where the effect of short-wave and long-wave solar radiation on construction surfaces is able to produce massive outdoor local overheating. Traditional solutions cannot always be applied in urban historical canyons, where the exteriors of buildings cannot be modified due to preservation. Here, the capability of innovative cool materials to mitigate local microclimate of historical urban canyons is investigated. A preliminary experimental characterization of the materials is performed. A numerical simulation of the microclimate effect generated by the application of such materials is performed. Results show that the proposed materials improve the microclimate without neglecting preservation constrains. Such materials set the best scenarios in terms of thermal comfort, by enhancing albedo on canyon surfaces. Their application on the vertical surfaces of narrow canyons can lead to deleterious effects on outdoor thermal comfort. Such findings are confirmed by PMV and MOCI analyses. Energy efficiency solutions may be effectively implemented in historical districts, opening the doors to other tailored solutions, such as integrated renewables, to make these environments more sustainable and comfortable.