Environmental impact of the variations in solar reflectance index values of some selected dimension stones due to cyclic thermal shock

Abstract

AbstractNatural stones are widely used environmentally appropriate building materials as dimension stone both for exterior cladding and floor coverings in urban areas. Depending on their solar reflectivity, these materials may absorb more solar radiation, especially with noontime summer sunlight exposure, which may cause both increasing cooling costs in commercial buildings and overheating of a city with the formation of urban heat islands. Solar reflectance index (SRI) is defined as the ability of a surface to reject solar heat which tends to change with physical, chemical and biological degradation processes by varying solar reflectance (SR) and thermal emissivity (TE) values. Weakening of the stone matrix structure by physical degradation mechanism, such as thermal shock (T-S) cycles mostly have significant impact on SRI. Within the scope of this study, SRI values were calculated before and after cyclic T-S by measuring the optical properties such as SR and TE values of 30 selected sedimentary and metamorphic originated carbonate-based natural stone types. The changes in surface properties such as color, roughness, and gloss, that may have an impact on the SRI values were also analyzed. In addition, a multivariate regression analysis was established to predict SRI value from such properties with a high degree of accuracy. Finally, it was found that, initial SRI values of 9 natural stone types (mostly metamorphic originated) have been increased considerably by cyclic T-S and tend to increase their ability to reduce urban temperatures by higher SRI values, one of the most important selection criteria in energy consumption for natural stones.