An innovative type of air conditioning system was developed at the Fraunhofer Institute for Building Physics IBP. The chilled water wall is a device, which cools and dehumidifies office rooms, conference rooms or hotel lobbies in a remarkably pleasant way. In a thin film, chilled water is flowing down a vertical wall. The water film has a temperature well below the dew point temperature of the room air. This results not only in effective and draft-free radiation cooling, but also, the device reduces indoor humidity, since air moisture condensates on the water surface and runs off, thus avoiding the risk of mold growth.