Multizone cooling model for calculating the potential of night time ventilation.

One of the options to increase the energy efficiency of buildings in the cooling season, is to extract heat from the building envelope during the night by natural or forced ventilation. The exploitation of this technique by architects and designers requires the development of guide lines and a predesign tool showing how the potential cooling power depends on the influence of opening sizes and positions and on the interaction with the thermal mass. While a single zone model is sufficient to estimate rougly the heat extracted fiom the building, a multi zone extension allows one to predict the distribution of air and wall temperatures and therefore the distribution of cooling power over the air flow path (when the zones are ventilated in series). A zonal cooling model based on the principles of mass and energy conservation and coupling ventilation with both heat transfer and a thermal model for the walls. The parameters of the ventilation model are the size and position of the openings, the stack height, and climatic parameters like temperature swing and wind characteristics. The heat transfer is parametrized by the exposed surface area of thermal mass, while the heat storage for heavy weight constructions is only characterized by both that surface area and the thermal effusivity of the exposed wall material. The predictions are compared with measurements for a simple flow path configuration.