This paper measured the temperature and the humidity of the air in the ceiling depending on the operation and non-operation of an air-conditioner and a ventilation system for ceilings only. It was found that: in case of the only air-conditioner on and ventilation off appropriate thermal environment was maintained in the swimming pool and in the ceiling; and in case of the air-conditioner off and the ventilation on the relative humidity in the ceiling was maintained under 62%, so it was concluded that dew condensation gives a no influence on the safety of the inside of the ceiling. In case of the air-conditioner off and the ventilation off the relative humidity of the air in the ceiling was increased to about 78%. In this paper the quantity of energy consumption, was also measured depending on the operation of the air-conditioner and the ventilation system. It was found that the energy consumed for the operation of the air-conditioner per hour was about 625 times greater than that of the ventilation system.