In hot and humid region, air-conditioning is increasingly used to attain thermal comfort. Air-conditioning is highly energy intensive and it is desirable to develop alternative low- energy means to achieve comfort. A comparison of overall cost reduction in providing thermal comfort in a building by the use of (i) Wetted roof surface and (ii) Painted roof, against bare roof surface .For this purpose M.R reading hall of M.A Library A.M.U Aligarh is chosen as the subject building and the mathematical model available in the literature have been used for prediction of roof outside surface temperature and consequent heat transmission in the building through the roof. Calculations were carried out for a typical summer day of May for Aligarh (India). The difference between the wetted & bare roof and painted & bare roof is compared to conclude that wetted roof surface cooling technique is much better than the painted roof surface.