Solar control of extensively glazed facades : a computer method for predicting the effects of various devices and building’s thermal inertia

Many temperate climates, like most Italian ones, are characterized by considerable daily temperature ranges. In these cases, the thermal inertia of the building has a significant influence on the management of solar and internal heat gains; then on the energy demand for HVAC, this is especially true in the cooling period. Winter and summer requirements regarding thermal inertia may be in conflict with each other, in particular when the use of the building is discontinuous, as in the case of offices. A lower thermal inertia can allow a more rapid heating in the morning and minor nocturnal losses during the winter, whereas a higher inertia may allow a slower daytime heating and a better exploitation of night free cooling during the cooling period. In this study, a typical office room has been studied by means of computer simulations. The only external wall of the room faces south and is entirely glazed; therefore, it requires the use of some device for solar control. Relatively to this room, the combined effects of some different solar control strategies and three constructive technologies, characterized by different thermal inertia, have been explored. A first strategy is based only on the use of an internal reflecting and diffusing screen, a second on the use of external movable slats, a third on the use of small slats inserted between the glasses. Strategies based on the two types of slats can be integrated with the use of an internal diffusing screen. Computer simulations were performed using a software that allows simultaneous analysis of energy and comfort issues, automatically taking into account any control action aimed at maintaining the thermal and luminous comfort. They were used climatic data of Gorizia, in the North East of Italy. Simulations results show that the thermal inertia has a great influence on energy demand and on thermal comfort. The strategy based only on the inner screen is the least advantageous from all points of view. Between the two types of slats, the external ones allow a better thermal comfort, while the others provide a better visual comfort.