Solar Control in Buidings with Large Glazed Surfaces : The Role of Internal Screens

A large part of new office buildings is characterized by extended external glazed surfaces, generally located without any care about orientation. Without a suitable solar control strategy, this fact implies a series of well-known problems: high-energy demand and consequent carbon dioxide emissions for HVAC, as well as thermal and luminous discomfort. Moreover, if the working room is large, the values of physical parameters influencing comfort are relevantly variable from point to point. The best way to control entering solar radiation is based on the use of external movable elements, such as slats or screens. However, in some winter periods, it would be appreciated to promote the collection of solar radiation in order to contribute to cover heating loads. In this case, the use of internal diffusing or redirecting elements (i.e., blinds or venetian curtains) is necessary to avoid glare phenomena. The physical properties of these elements influence the room thermal balance, and their temperatures influence indoor thermal comfort conditions, particularly for the nearest occupants. This work tries to identify, by means of computer simulations, optimal physical properties of some kinds of internal diffusing screens. A case study has been examined: it consists in a medium size office room