Cool colored coatings for passive cooling of cities

The heat island effect is becoming increasinglymore intense in urban areas causing thermal discomfort,increased energy demand and acceleratingthe formation of harmful smog. The mitigationof the heat island effect can be achievedby the use of cool materials. Cool materials arecharacterized by high solar reflectance and infraredemittance values. In the framework ofthis study, the performance of prototype coolcolored coatings, developed at the National andKapodistrian University of Athens, using nearinfrared reflective color pigments is reported, incomparison to color-matched, conventionallypigmented coatings. The solar spectral propertiesand the infrared emittance were measuredand the surface temperature of the tested coatingsapplied on concrete tiles was monitored,using surface temperature sensors and a datalogging system. The experimental results indicatesignificant success in developing cool coloredcoatings. It was found that all the coatingscontaining infrared reflective pigments havehigher solar reflectance values and lower surfacetemperatures than those of the standardcoatings. Cool colored coatings can be used onbuildings (roofs and walls) and other surfaces ofthe urban environment or they can be used tomanufacture other cool colored building materials.Furthermore, this paper presents the resultsof a modelling study, undertaken for the case ofAthens, Greece, that attempts to asses the impactof large scale increases in surface albedo,resulting from the use of cool materials, on theambient temperature. The results of this studycan help to promote the adoption of high albedomeasures (the use of cool materials) in buildingenergy codes and urban planning regulations.