Research Article Building Thermal, Lighting, and Acoustics Modeling E-mail: svera@ing.puc.cl Potential of perforated exterior louvers to improve the comfort and energy performance of an office space in different climates Daniel Uribe 1,3 , Waldo Bustamante 2,3 , Sergio Vera 1,3 () 1. Department of Construction Engineering and Management, School of Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile 2. School of Architecture, Pontificia Universidad Católica de Chile, Santiago, Chile 3. Center for Sustainable Urban Development, Pontificia Universidad Católica de Chile, Santiago, Chile Abstract Fully glazed building façades often experience high solar heat gains and daylight transmission, resulting in high cooling energy consumption and visual discomfort. The objective of this study was to investigate the potential of perforated exterior louvers for controlling solar heat gains through a fenestration system, providing visual comfort to the occupant and improving the energy performance of an office space in distinct climates (tropical, semiarid, humid subtropical, continental) based on integrated thermal and lighting simulations. The louvers evaluated have 0%, 5%, 10%, 15%, 20%, 25% and 30% perforations with 120 and 240 mm louver spacing. This study demonstrates the potential of perforated exterior louvers for controlling solar heat gains and daylight transmission to improve the visual comfort of the occupant and the building energy consumption. Since perforations can significantly influence office performance and occupant comfort, it is crucial for an evaluation of this type of louver to be completed in the early design stages with integrated thermal and lighting simulation tools that are able to address the complex thermal and optical properties of the louvers. Louvers with 120 mm spacing and 5%–20% perforations reduce office energy consumption by 15%–63% (depending on the city) compared with an unshaded window while meeting the visual comfort criteria (sDA300/50% between 96% and 100%, ASE4000/400h of 0% and DGPs perception class A). Additionally, the percentage of perforations and spacing of louvers significantly impact the evaluated performance criteria. CFSs fully cover the window but have evenly distributed perforations outperform shading devices with larger spacing between louvers and louvers without perforations. Keywords perforated exterior louvers, visual comfort, solar heat gains, energy performance, daylight, integrated building simulations Article History Received: 12 May 2017 Revised: 2 February 2018 Accepted: 5 February 2018 © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018 1 Introduction The largest energy-consuming sector is buildings, which represent 32% of the global energy consumption in 2010. For this reason, the building sector causes one-third of greenhouse gas emissions (Lucon et al. 2014; OECD/IEA 2013). Therefore, building energy efficiency plays a key role in global temperature and climate change. The building sector includes the residential and commercial sub-sectors. Among commercial buildings, office buildings consume a significant fraction of end-use energy. For instance, they consume 20.97% and 17.82% of all energy for commercial buildings in Canada and USA, respectively (IEA 2012; NRC 2013). Office buildings use energy mostly for heating, cooling and lighting. Today, there is a worldwide trend to design and build fully glazed office building façades that are independent of the climate and use of the building, which causes excessive solar heat gains (SHGs) and daylight transmission into indoor spaces. High SHGs increase cooling energy consumption. Excessive daylight transmission produces visual discomfort, so the occupants tends to close window shading systems (i.e., indoor venetian blinds), which might cause higher lighting and cooling energy consumption. Figure 1 shows the Titanium Tower, located in Santiago, Chile (S33°22’, W70°46’), which is a perfect example of this worldwide BUILD SIMUL https://doi.org/10.1007/s12273-018-0435-y