Building mass and ventilation working together to reduce cooling loads

Integration of building components and ventilation systems is an effective way to control thermal loads, especially cooling loads. The key point of the system which has been studied in this paper is a special hollow building slab which allows the penetration of variable ventilation air flows. The ventilation rate may be adjusted following a specific control strategy, in order to activate the thermal mass of the slab, and enhance the free cooling effect in the night time. In order to evaluate the performance of this system, a dynamic feedback model has been implemented using a dedicated software tool (Simulink). The main advantage of this software is that it is particularly suitable to simulate feedback control systems, in which the input data (e g, flow rate) may be generated by the previous time step outputs (e g, indoor/outdoor air temperature) . The model describes the thermal flows within a reference room in which the special component is installed, along with the ventilation system. Different building structures (light/heavy) and ventilation control strategies have been
analysed for a typical summer period in Northern Italy (Po Valley). The tests have shown that cooling energy savings up to 50 % may be achieved respect to a traditional building fabric assisted by a constant ventilation mechanical system