The present paper deals with the application of 4500 m 2 of reflective pavements in an urban park in the greater Athens area. The aim was to improve thermal comfort conditions, reduce the intensity of heat island and improve the global environmental quality in the considered area. To our knowledge, this has been the largest application of cool pavements in urban areas in the world. To evaluate the thermal impact of cool paving materials, specific and detailed measurements of the climatic conditions in the park have been performed before and after the installation of the new materials. Validated computerized fluid dynamics techniques have been used to homogenize the boundary conditions occurring during the two experiments and to perform direct comparisons of the climatic quality in the park. It was estimated that the use of cool paving materials contributes to the reduction of the peak ambient temperature during a typical summer day, by up to 1.9 K. At the same time, the surface temperature in the park was decreased by 12 K, while comfort conditions have been improved considerably. It is concluded that the use of reflective paving materials is a very efficient mitigation technique to improve thermal conditions in urban areas.

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The urban heat island effect and its consequences is one of the most important problems cities worldwide have to face in an effort to become more sustainable. This paper presents a study of a major open area in a densely built and populated area in the centre of Athens that was part of a Municipality of Athens program to improve thermal comfort conditions in open spaces. The bioclimatic rehabilitation design process was based on a specific strategy involving detailed monitoring of the thermal characteristics and climatic conditions in the area, extensive analysis of the results in order to define the problem, design and use of efficient passive cooling techniques (cool materials, green spaces, solar control and earth to air heat exchangers), and the use of advanced simulation tools to evaluate and optimise the planed microclimatic improvements. The results indicate that the proposed measures contribute to a decrease in local temperatures of up to 2°C for summer conditions. Practical application: • The knowledge on perceptions of microclimate in outdoor space can serve as a basis for urban spatial design. • To evaluate the application of cool materials in public urban squares. • Strategies to improve local microclimate with monitoring and modelling the design features.

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