High performance building envelopes with retro-reflective materials

Highly reflective materials have been proposed as a strategy for energy consumption reduction in buildings and outdoor comfort improvement (i.e. urban heat island mitigation). Common cool materials’ high reflectivity allows to reduce surface temperature and thus cooling energy consumption in buildings. However, since they reflect energy diffusively in the hemisphere, most of the energy can be trapped within the urban canopy, in case of deep urban canyons and multiple reflections between buildings of different heights. Retro-reflective (RR) materials are proposed as new highly reflective materials for the building skin since they reflect most of the striking energy backward towards the incoming direction. RR directional properties allow to reduce the amount of energy trapped within urban canyons and urban canopies. Several studies are focused on the properties and beneficial effects of RR materials for building application. In this work the properties of retroreflective materials are presented. An analysis of the state of the art of materials for building application is proposed. Furthermore, opportunities and potentialities of RR materials compared to common cool materials are discussed from energy and environmental point of view. A discussion is proposed about their effectiveness and convenience in different urban patterns and for different optic properties and global reflectance.