Lighting Implications of Urban Mitigation Strategies through Cool Pavements: Energy Savings and Visual Comfort

Cool materials with higher solar reflectance compared with conventional materials of the same color are widely used to maintain cooler urban fabrics when exposed to solar irradiation and to mitigate the Urban Heat Island (UHI). Photo-catalytic coatings are also useful to reduce air pollutants. Many studies related to these topics have been carried out during the past few years, although the lighting implication of reflective coatings have hardly been explored. To investigate these aspects, reflective coatings were applied on portions of a road and intensely analyzed in a laboratory and on the field. The applied cool coatings were found to have much higher solar and lighting reflectance than the existing road, which lead to lower surface temperatures up to 9 degrees C. Non-significant variations of chromaticity coordinates were measured under different lighting conditions. However, these materials showed a relevant variation of directional properties depending on the lighting and observation conditions with respect to conventional pavements. The optical behavior of these materials affects the uniformity of visions for drivers and requires ad-hoc installation of light sources. On the other hand, potential energy savings of up to 75% were calculated for the artificial lighting of a reference road.