Experimental validation of retroreflective materials in urban environments

The use of retro-reflective materials in building envelopes and urban pavements can contribute to the mitigation of urban canopy overheating phenomenon. Diffusive and directional covers must be applied considering the distribution law of their reflective direction as well as the intensity of the reflection. Focusing on the visible range of solar radiation, this research topic has been investigated by the authors arranging a custom-made radio-photo goniometer allowing the measure of the retroreflective potential of directional samples. Study demonstrates, by lab measurements, the distribution law of reflected solar radiation by some directional samples, looking at the amount of the reflected radiation along the normal direction. As reference, a diffusive reflective sample (DIFF) is also characterized with the same lab equipment. The normal reflectivity of the samples has been measured and calculated using a model proposed by Rossi et al. from literature. Spectral behaviour of the RR materials with % R > 70 for all RR samples with less size glass beads and diffusive showed less high %R and spectral deviation remained <5 %. The measured and calculated values are in same order of magnitude, and the experiments shows that the distribution law proposed is near to the real scale experimental results. The trend line and statistical analysis report the validation of analytical model. The regression model shows R 2 value equal to 0.57 which is due to minute error with handling and experimentation with manual human operator. The RR3 and RR5 is seen aligned which satisfies the validation of model experimentally. The model verification is crucial as the RR materials in future are proposed to be applied as building facades skin for tackling urban overheating.