This paper presents the performances of Acetaldehyde and R22 refrigerant as working fluids for a closed loop pulsating heat pipe (CLPHP) cool roof system. We used two working fluids one after the other as the circulating fluids in a 404mm by 350mm roofing for an enclosure of 552mm by 350mm dimension. We used water as the cooling agent for the fluid condensation. The results showed that for the two working fluids, there is an average temperature difference of 3°c between the inside and the outside of the room. The discovery underscored the capability of the CLPHP cool roof system, showcasing its potential simplicity, cost-effective, and efficient alternative solution for improving thermal comfort in buildings located in tropical regions instead of the use of thermal mass walls.