In many cases the thermal conditioning of buildings is based on an optimization of the building envelope (walls, windows) with regard to insulation and solar transmission, combined with a heating/cooling and/or ventilation system. Instead of using full air conditioning, it may be possible to condition a space with embedded pipes circulating warm or cool water in the concrete slabs between the floors in a multistory building. This will not only provide direct heating or cooling over the surface of the slab but also an additional effect due to the thermal storage capacity of a concrete slab. This paper presents the results of a dynamic computer simulation of such a system. The results showed a significant improvement of thermal comfort by reducing the annual maximum operative temperature by 10 K compared to no cooling. Annually more than 60 kWh/m2cooling could be obtained.Units: SI