cool roofs

Maintaining thermal comfort in buildings has become a big challenge in developing countries. Cool roof or high reflective/emissive roof reduces absorbed building solar energy, roof surface temperature to reduce energy consumption and maintain thermal comfort. However, the impact on buildings thermal performance located in hot-dry climate and dusty conditions is not well-known.

Increasing roof reflectance reduces absorption of solar radiation, roof surface temperatures, and heat flux in the building interior. At the building level this leads to savings in air-conditioning energy consumption and increase in indoor comfort. At the macro level it helps in mitigating Urban Heat Island effect and reduces net solar radiation absorbed by the earth, lowering local air temperature and pollutant formation, and reducing global warming. Various studies have demonstrated energy savings in buildings using cool roofs.

The urban climate of high-density areas is often affected by an increase of the air temperature known as Urban Heat Island (UHI) phenomenon. 
UHI is strongly influenced by the solar reflectance of conventional materials used for building envelope and urban coatings, i.e. streets and square pavings. 
The present work proposes an original method to predict the temperature of both facades and local air mass on urban scenarios. The effect of changes on coatings may also be estimated.  

The present study aims at investigating different methodologies and standards for measuring and calculating solar reflectance and infrared emittance, the two main properties characterizing cool roofing materials. In order to achieve this goal, an interlaboratory comparison testing has been set up among several laboratories that are members of the European Cool Roofs Council.

Heat island which is the most documented phenomenon of climatic change is related to the increase of urban temperatures compared to the suburban. Among the various urban heat island mitigation techniques, green and cool roofs are the most promising since they simultaneously contribute to buildings’ energy efficiency. The aim of the present paper is to study the mitigation potential of green and cool roofs by performing a comparative analysis under diverse boundary conditions defining their climatic, optical, thermal and hydrological conditions.