SIMULATION FOR FAÇADE OPTIONS AND IMPACT ON HVAC SYSTEM DESIGN Athanassios Tzempelikos and Andreas K. Athienitis agtzemb@alcor.concordia.ca athiena@alcor.concordia.ca Centre for Building Studies Department of Building, Civil & Environmental Engineering Concordia University 1257 Guy Str., H3H 1H5, Montreal, Quebec, Canada Tel.: +514-848-8791, Fax: +514-848-7965 ABSTRACT This paper presents a simulation study employed for the optimization of the building envelope for a new university building located in Montreal (latitude 45 0 N). The study involved simulation of façade design options, taking into account maximization of daylight, reduction in electricity consumption for lighting and optimal control of solar gains. Combinations of motorized shading devices in conjunction with controllable electric lighting systems are investigated in detail. Transient simulations also considered the impact of motorized shading and light dimming on HVAC system sizing and energy consumption for heating/cooling. The resulting energy savings and thermal comfort using an optimum design strategy are discussed. INTRODUCTION The area of fenestration in buildings is continuously increasing, driven by two factors- first the higher demand for buildings with much daylight, and second the development of advanced windows with predictable or controlled solar transmittance characteristics (e.g. electrochromic coatings, motorized shading) and high thermal resistance. The increased fenestration areas often result in highly varying heating and cooling loads throughout the year, especially when inadequate amounts of thermal mass are employed. The fragmented nature of the building process, in which no member of the design team considers the overall optimization of the indoor environment, further compounds the problem. Different types of dynamic building envelope systems have recently been studied and employed in buildings in order to achieve a better performance. The main purpose of these devices is to optimally control solar gains and create a high quality indoor environment. The design of such systems is a complex task; daylighting, shading, peak heating and cooling loads and electric lighting together with their control strategies should all be taken into account when designing a façade. Since the above parameters are interrelated, an integrated approach must be followed in order to attain an optimal solution. The situation is more complex for facades with high solar gains. In this case, shading provision should be considered as an integral part of fenestration system design. One solution is the use of advanced windows with innovative fenestration systems and motorized shading devices (Rosenfeld et al 2001, Athienitis & Tzempelikos 2002). They can block direct sunlight and allow diffuse light into the room, thereby eliminating glare and creating a pleasant luminous environment if they operate optimally. Dynamic control of shading devices, daylighting systems, electric lighting and HVAC system components may lead to minimization of energy consumption for lighting, heating and cooling (Lee et al, 1998). At the same time, good thermal and visual comfort can be achieved under continuously varying outside conditions. The objective of this paper is to investigate different façade design options for a new building to reach an optimum solution, based on all factors mentioned above. The effects of each parameter on energy efficiency and human comfort are studied simultaneously. Human control of some of the components is also discussed. SIMULATION METHODOLOGY The 17-storey-high building has two main unobstructed facades facing southwest and southeast. The total floor area is about 53000 m 2 while the floor area covered by perimeter spaces is 5000 m 2 . The first decision is the fraction of glazing area of the façade. This should be decided in conjunction with the thermal properties of the curtain wall and the type of glazing. The thermal resistance of the curtain wall was set to 3 RSI, to meet energy code recommendations for Montreal. Then a typical floor was selected for energy Eighth International IBPSA Conference Eindhoven, Netherlands August 11-14, 2003 - 1293 - - 1301 -