Using of false ceilings (FC) for decoration and covering different ducts in modern buildings is spreading so much nowadays. This paper tries to find a new employment and other benefits for using false ceilings (FC).A one dimensional transient mathematical model has been established to study the effects of using false ceiling on reduction of heat gained from concrete roof of controlled temperature space. The effect of using false ceiling (FC), with and without adding reflector sheet on its upper side facing to concrete roof on the room cooling load is studied by modeling and solving the transient heat transfer processes in the different components of the space. The results showed that using of false ceiling only without reflector sheet reduces heatgain introduced to space through 24 hours by 66.8%, while using of false ceiling with reflector sheet increases the reduction percent of heat gained from concrete roof to be 81.6% for the same period.