Passive solar ventilation

As the twenty first Century approaches, more emphasis is given to energy conservation and passive systems in order to maintain a clean environment. New strategies showed the necessity of reviewing some design elements and their evaluation techniques. Architects should seek to increase their understanding of the correlation between the natural and the built environment. In the recent years, many architectural styles started to emerge in Egypt without paying enough attention to their suitability to the environment and climate. The pitched roof is increasingly used in both summer resorts and new residential developments and settlements in the north west coast of Egypt on the Mediterranean. These locations are characterized by a temperate climate with excessive heat and humidity rates during summer. In general, higher air velocities and numerous air changes per hour can improve comfort conditions in a humid climate. A pitched roof has an advantage of accommodating a passive solar chimney collector that induces the natural ventilation depending on the thermal difference between indoor and outdoor air temperatures. Air flow rates increase if the height between inlet and outlet is increased. Meanwhile, when stack height is increased for a roof with a fixed area, tilt angle increases and solar heat gain factor facing the same solar altitude decreases. Within the mentioned context, this paper intends to examine the optimum tilt angle for a solar chimney system applied to the study area (32 deg. north latitude) that compromises between solar heat gain factor and stack height to insure the best ventilation performance. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.