Predicting the solar evaporative cooling performance of pervious materials based on hygrothermal properties

Pervious pavement has been regarded as an effective technique for both water storm management and overheating prevention. However, compared with its widely recognized permeability capability, its solar evaporative cooling performance remains under debate after post-occupancy evaluation; thus, it is essential to predict the solar evaporative cooling ability before practical use. Hygrothermal properties (i.e., albedo, water absorption, and water retention properties) are key factors that affect the solar evaporative cooling effect of pervious materials and could be extracted as predictive indicators. However, an approach for assessing the water absorption and retention properties has not been well studied. Therefore, this study aimed at characterizing a feasible method for testing water absorption and retention properties of pervious materials as well as the influence of albedo on the solar evaporative cooling performance. Five widely used pervious materials were selected as research subjects, and three hydrological test methods, including the integral immersion test, partial immersion test, and rainfall simulation test, were conducted for comparing the feasibility of measuring water absorption and retention properties. Furthermore, the solar evaporative cooling performance of pervious materials with high and low albedo was also investigated. The results reveal that the partial immersion test has the highest accuracy for evaluating the water absorption and retention properties of pervious materials. Although the high albedo could weaken the evaporation rate, pervious materials with high albedo could also achieve better solar evaporative cooling performance. The results of this study support the proper selection of pervious materials to alleviate urban overheating.