This Information Paper provides an introduction to cool roofs: what they are and how they work, their benefits and their application in the UK. The generic term 'cool roofs' describes a range of roof types incorporating external finishes that have high levels of solar reflection and emissivity. By effectively reflecting and re-emitting incident solar energy, cool roofs mitigate excessive interior heat gains, reducing the need for air-conditioning and improving energy efficiency. Research demonstrates the contribution made by cool roofs to combating the urban heat island effect, thereby helping to reduce the incidence of urban smog formation. (A4,12pp) Contents Background What is a cool roof? How do cool roofs work? - Reflectance - Emissivity - Solar reflectance index Cool roofing products - Flat roof applications (Single-ply, Liquid-applied coatings, Maintenance of flat roofs) - Pitched roof applications (Reflective tiles and shingles, Metal coverings) Benefits of cool roofs - Urban heat islands (Causes, How cool roofs help mitigate the UHI effect) - Reducing cooling requirements (Evidence base) Cool roofs in the UK Conclusions and recommendations References