A construction company developed the building technology to decrease the room temperature inside a plant by about 10 degrees centigrade only by natural ventilation. Sumitomo Mitsui Construction worked out the system that takes outer air cooled down by the humidification and refrigeration function by water sprinkling and emits the hot air inside the plant through the exhaust smoke stack. This system is designed for medium-sized manufacturing companies. It installs a louver made up of horizontally-aligned sloping boards in the air supply side. The humidification and refrigeration function created by the water sprinkling near the louver cools down the air inside the plant, and the cooled air goes down to decrease the temperature of the work area. At the same time, the hot air goes up accordingly, and will be discharged automatically through the exhaust smoke stack heated by the exhaust heat of the plant. The work area of cardboard manufacturing plants is as high as 40 degrees centigrade in summer, and the new technology successfully decreased it to 33 degrees centigrade. The construction cost is 15 million yen for a medium-sized plant with an area of 1,500 square meters. It takes about a week to install the system.