The objective of this paper is reduced the electrical energy which used in air-condition system by replaced the common roofing system by the another which more suitable for hot climate area. The researcher was build (1x1x3)m sample room at 3rd floor in building at Baghdad city (33.2 °N) for 200mm polystiran thermal insulation for other room surfaces and air-conditioner of 0.5 Ton of refrigeration capacity is used to maintain the standard thermal comfort, the roof thermal behavior study for 15 hr/day, at day 21 from five each months (Jan, March, June, July & September). It was found the suggested roofing system reduced the dead load by 300kg/m2 and the electrical energy which used in air-conditioning system reduced by 37% when used open air gap was used, and become 30% when has used closed air gap has used and became 27% relation to ordinary system.