An integrated thermal and lighting simulation tool to support the design process of complex fenestration systems for office buildings

Abstract

Office buildings are greatly affected by solar heat gain and daylight transmission through fenestrations. External shading devices control the solar radiation transmission, thus they significantly influence building performance because of improving energy efficiency and visual comfort. Automated control systems for external shading devices to simultaneously control solar heat gain and indoor illuminance can minimize the energy use and provide visual comfort. To minimize the total energy consumption, building designers need the support of building performance simulation tools that can integrate the thermal and lighting simulations, such as mkSchedule. The main objective of this paper is to demonstrate the use of mkSchedule as a tool for supporting the decision-making process in the early building design stages using a case study of an office space with two different external and movable complex fenestration systems (CFSs) and controlled dimmed luminaires in four cities. The CFSs are controlled by the irradiance on the façade, and mkSchedule is used to determine the maximum allowable irradiance that minimizes the energy consumption while meeting the visual comfort criteria. The four studied cities are Montreal, Canada; Boulder, USA; Miami, USA; and Santiago, Chile. Two external shading devices are evaluated, a set of external perforated curved louvers and a set of venetian blinds. For each case, the visual comfort was assessed based on the spatial daylight autonomy (sDA) and the annual sunlight exposure (ASE) according to the Illuminating Engineering Society (IES) standard; whereas, the building energy performance was determined in terms of the sum of heating, cooling and lighting energy consumption. For the venetian blinds, the maximum incident irradiance threshold varied between 530 W/m2 and 610 W/m2; while this threshold varied between 290 W/m2 and 350 W/m2 for the louvers. This study demonstrates that mkSchedule is an effective tool for determining the performance of different CFSs in the early building design stages considering visual comfort criteria and building energy performance, thus it provides information not only to choose among different alternatives of CFSs and control algorithms, but also to set the main parameters of the control algorithm.