The creation of large impervious surface in urban and urbanizing areas have led to significant impacts on local climate, which is commonly known as urban heat island (UHI). In this study, porous pavements made of recycled sludge were examined as a way to control UHI by lowering the surface temperature. A novel image analysis technique was applied to quantify cooling effect of porous pavement materials without and with water. Although the porous pavement itself has smaller heat capacity than the natural soil, supplying water to the pavement decreased its surface temperature. At its highest point, the difference in surface temperatures without and with water was more than 10 oC. The water was supplied either from the top of the pavement or from the bottom of the pavement using the capillary effects. In both cases, pavement temperature was effectively lowered. The cooling effect of pavement by surface coating using epoxy-based polymers was negligible because surface pores were blocked. Field tests also confirmed the cooling potential of porous pavements.