STATIC AND DYNAMIC DAYLIGHT CONTROL SYSTEMS: SHADING DEVICES AND ELECTROCHROMIC WINDOWS Franco Gugliermetti, Fabio Bisegna Department of Fisica Tecnica, Faculty of Engineering University “La Sapienza”, Rome, Italy e−mail: fabio.bisegna@uniroma1.it ABSTRACT This paper analyses the office demand connected to the use of different dynamic window and lighting control systems with the aim to optimize their usage aspects and characteristics from both visual and energy efficiency viewpoints. The approach is based on an improvement of the non-commercial hourly simulation program IENUS. Results are referred to a typical office located in Mediterranean climate. INTRODUCTION Shading devices always represented fundamental systems to control the incoming of the natural light with two main purposes: improving indoor visual and thermal comfort, reducing HVACs and artificial light systems energy consumption. Industries in these last years have developed and produced different types of transparent materials and lighting control systems to take full advantage of the energy saving potential coming from daylight. ElectroChromic (EC) “dynamic” windows, that can change their transparency properties in response to control parameters integrated in a natural and artificial lighting control system, could represent a way to improve both environmental quality and energy use efficiency. The possibility to integrate EC materials in building windows, as a part of a commercial light control system, appears nowadays very promising, as EC devices seem to be ready for commercialization (Granqvist, 1993, Granqvist et al., 1998, Lampert, 2000). Different lighting control systems are used to control lamp light outputs and natural light. Natural lighting controls by automatic mini-internal blinds to large exterior rolling louvered shutter systems are available and popular in office buildings due to their adjustability and ability to reflect light. While artificial light systems are dimmed or switched following daylight variation to keep design lighting levels as constant as possible during all the maintenance cycle of the lamps. Commercial control systems can operate with algorithms that can realize either a closed-loop integral control or an open-loop proportional control. ElectroChromic (EC) and light control systems try to realise indoor comfort and energy saving by approaches, that are different in complexity, costs and results. Besides, a good coordination among them could produce better performances. Several research groups all over the world have developed a lot of studies over the last decade. The aim was generally to characterise the possibilities and the improvements introduced by these new technologies (Moeck et al., 1998, Sullivan et al., 1994 and 1996, Yoong and Tulloch, 2000, Karlsson et al., 2000, and Karlsson, 2001, Gugliermetti and Bisegna, 2003, 2005). But a study on both the visual comfort and energy efficiency aspects, considered in comparison with traditional window systems equipped with internal shadings controlled by a linear strategy, is still lacking, as it is still lacking a guideline for the selection of the proper window system considering all the possible visual and energy aspects. This paper analyses the office space energy demand connected to the use of different EC and light control systems for office buildings located in Mediterranean climate, with the aim to optimise their usage aspects and characteristics from both visual and energy efficiency viewpoints. On/off and linear control strategies to change the transparency of EC systems from clear to dark state, and to close the indoor curtains are here presented. Dimming and on/off control strategies are also considered for managing the artificial lights. The paper represents only a step of a wide research aimed at defining several guidelines for the selection of the proper window system, also considering innovative windows, for each specific situation. The approach is based on an improvement of the hourly simulation program IENUS (Integrated ENergy Use Simulation), a non–commercial program developed to assess the building energy demand of simple spaces, taking into account the integration between visual and thermal aspects. Ninth International IBPSA Conference Montréal, Canada August 15-18, 2005 - 357 -