Experimental analysis and optimization of outdoor curtain materials for solar protection as a solution for urban heat island mitigation and thermal comfort improvement

Urban Heat Island (UHI) is a growing phenomenon taking place in dense urban environments and it is due to the lack of green areas and to the presence of built surfaces, which are typically characterized by low solar reflectance and high infrared emissivity. Furthermore, UHI is exacerbated by the Urban Heat Canyon configuration and Inter-Building effect, consisting in multiple reflections of the solar radiation, which remains entrapped inside the urban canyon. For that reason, built surfaces have a great potential in urban microclimate enhancement and UHI mitigation, particularly through the improvement of materials’ solar reflectance and thermal emissivity properties. In this context, outdoor tensile structures, such as curtains and awnings, could represent an effective way for UHI mitigation and human thermal comfort enhancement, through the selection of materials with high solar reflectance on the external side of the curtain and low infrared emittance downwards. The present work is focused on the characterization of a novel glass fibre-based material for outdoor curtains and awnings in terms of solar reflectance, thermal emittance and angular reflectivity. Findings show that the tested material reveals a good solar reflectance, while a high thermal emittance has been detected. For what concerns directional reflectivity, all samples present a retro-reflective trend for incident light angles near the perpendicular, while a specular tendency occurs for incident light directions near the horizontal.