Passive cooling of the built environment - use of innovative reflective materials to fight heat islands and decrease cooling needs

Cool materials have high solar reflectance (high ability to reflect sunlight), high thermal emittance (high ability to radiate heat) and stay cool in the sun. Various cool coatings have been developed recently. This paper analyses a prototype low cost cool coating using lime which shows a 15% increase in reflectance compared with a standard cool coating. Also, the ageing effect of cool coloured and white coatings are studied while they are exposed to outdoor conditions. The study shows that there is an attenuation of the white coatings' spectral reflectance while the cool coloured coatings demonstrate almost negligible loss in the visible range, thus maintaining their initial appearance. The infrared emittance of the cool and cool coloured coatings is not significantly changed by the outdoor exposure of the samples.