Evaluation of a parametric model and building simulation for design of passive cooling by night ventilation

At the new institute building of Fraunhofer ISE, both mechanical and free night ventilation is used for passive cooling of the offices. The results from a monitoring of room temperatures in 21 office rooms during summer 2002 show that room temperatures exceeds 25 C in less than 8 % of the working hours, even at high ambient air temperatures. In two offices, experiments were carried out in order to determine the efficiency of night ventilation dependent on air change rate, solar and internal heat gains. During the experiments, meteorological data, air change rates, air temperatures (incl. three-dimensional temperature field), surface temperatures (floor, ceiling, window, and internal wall) and the operative room temperature (globe thermometer) were measured. The aim is to identify two characteristic building parameters, i.e. the thermal loss factor H and the solar aperture G. Though the night ventilation effect is described only by the thermal loss factor H, the solar aperture G is
necessary to determine the complete energy balance for the room. Thus, the night ventilation effect can be separated from other terms in the energy balance. The experiments (one room with and one without night ventilation) are evaluated by using both a parametric model and the ESP-r building simulation programme. While the results from the building simulation match the measurements but deals with many input parameters, the parametric model deals only with two building characteristics and few weather data but does not agree well with measurements at each time step. Therefore, both models are merged in order to develop a method for data evaluation in office buildings with night ventilation.