Sensitivity Analysis of Skylight and Clerestory Design on Energy and Daylight Performance of a Retail Building

2018 Building Performance Analysis Conference and SimBuild co-organized by ASHRAE and IBPSA-USA Chicago, IL September 26-28, 2018 SENSITIVITY ANALYSIS OF SKYLIGHT AND CLERESTORY DESIGN ON ENERGY AND DAYLIGHT PERFORMANCE OF A RETAIL BUILDING Yuan Fang1, Soolyeon Cho2 1Western Kentucky University, Bowling Green, KY 2North Carolina State University, Raleigh, NC eye functioning problems (Edwards & Torcellini, 2002). ABSTRACT The wavelength of light also influences many other Daylight and energy performance are essential for health issues, such as nervous system, circadian rhythms, sustainable building design. Skylights and clerestories and endocrine system problems (Edwards & Torcellini, are effective strategies for providing sufficient daylight 2002). while reducing building energy requirement. To identify The advantages of daylighting designs in different the most influential variables of the skylight and building types have been documented in various studies. clerestory design, a parametric design model of a retail Specifically, it is found that proper daylight design in building is developed and 1000 design options are retail buildings can increase sales (Heschong et al., randomly selected. Integrated daylight and energy 2002), improve customer satisfaction, and promote simulations are performed for each option to evaluate the productivity (Boyce et al., 2003). Skylight is an effective lighting and thermal loads simultaneously. The lighting and energy saving method, however, it is still performance indices for daylighting and energy not widely applied in the industry. Only approximately performance evaluation are Useful Daylight Illuminance 2–5% of commercial building floor space has sufficient (UDI) and Energy Use Intensity (EUI). Then, a skylight area (Lawrence & Roth, 2008). Therefore, it is sensitivity analysis is used to rank building design necessary to advise designers and practitioners on how variables according to their contribution to the variance skylight strategies impact the building’s energy loads of UDI and EUI. The design features of the optimal and and what is the most energy efficient design solutions. worst design options are also discussed. The calculation of energy savings from daylight system INTRODUCTION is a complex process. Daylight system can provide daylight illumination which results in a reduction in Daylight is a key component in sustainable building lighting and cooling loads; it can also transmit solar design because of its influence on occupant comfort, radiation and heat which results in an increase in cooling health, and building energy efficiency. This study loads and reduction in heating loads. Therefore, an focuses on the design of skylights and clerestories of a integrative approach is needed to calculate the various retail building. The purpose is to identify the best and influence of daylight system simultaneously. worst design options and design variables’ influence on daylight and energy performance. Parametric design in architecture refers to the modeling process of building geometry using parameters and Artificial light and natural light usually work together to functions. The advantage of parametric design over provide lighting in modern buildings. Natural light is an traditional design method is its ability to quickly essential part of the lighting system, because negative generate design alternatives. Parametric design effects on occupants’ health were found if artificial maintains dynamic links between parameters and lighting is the only light source (Stevens, 2001; Basso Jr, geometry defined by the parameters. The modification of 2001). Natural light can help to maintain occupants’ parametric values leads to simultaneous updates of the health, improve mood, reduce fatigue, and reduce building geometry. Once a parametric building model is eyestrain (Edwards & Torcellini, 2002). Full-spectrum developed, design alternatives can be rapidly generated light from the sun is the best source of light for human through the manipulation of parameters. Furthermore, eyes, however, most artificial light is only concentrated when parametric design is coupled with building in a certain portion of the spectrum, which may lead to performance simulation, building performance data of © 2018 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us). 157 For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE or IBPSA-USA's prior written permission. each design alternative can be obtained and utilized to identify and prioritize the most influencing design analyze their relationships. variables. Sensitivity analysis is a valuable tool for building performance analysis. Sensitivity analysis has been widely used to explore the building performance in various types of applications, such as building design, calibration of energy models, building retrofit, and impact of climate change on buildings (Tian, 2013). Based on the simulation data, sensitivity analysis is used to identify and prioritize the most influencing design variables. The objective of this study is to develop a simulation Figure 1 Integrated daylight and energy simulation framework which integrates parametric design, daylight Building variables simulation, and energy simulation, and to analyze the relationship between design variables and building A single-story retail building located in Atlanta, Georgia performance metrics. The research framework is applied is used as the case study building (Figure 2). The area of to the skylight and clerestory design of a retail building. the building is 2000 square meters, which is the typical The results indicate which design variables are the most size of a small supermarket. The building has a flat roof significant considering the daylighting and energy that is 6 meters high. Daylight in the building is provided performance. In addition, the optimal and worst design by both skylights and clerestories. The skylights are curb options of the case study building could provide mount skylights, which means the glazing is raised from references for designers and practitioners. the roof plane. The footprint of each skylight is a square shape, while the glazing is a rectangular shape with SIMULATION various length. The curb height on the south and north Simulation framework vary independently, thus the glazing can face the north or south of the sky. The skylights are laid out on a grid Figure 1 shows the research framework of this paper. on the roof. The number of skylights varies from 42 to The research process begins with developing parametric 50 depending on the shape of the building. The size of building geometry with 8 design variables. The each skylight varies from 0.25 to 2.25 square meters, parametric model is developed using Rhino and which is the typical size of a skylight component. Grasshopper. Grasshopper plug-ins Ladybug and Considering the skylight number and the skylight Honeybee are used for energy and daylighting modeling, dimension, the skylight to floor ratio varies from 0.5% to and the simulation process is executed in EnergyPlus and 5%. There are clerestories on the four facades of the Radiance. An integrated daylighting and energy building. The width of the skylight is same as the length simulation method is constructed to examine the heating, of the facade, while the heights of the clerestories vary. cooling, and lighting loads simultaneously. A The top border of the clerestory is fixed on the top of the daylighting simulation runs first to calculate the façade, so the height of the clerestory depends on the illuminance at the lighting sensor positions for every location of the bottom border. hour in a year. A certain percentage of artificial light is turned off or dimmed depending on the daylight The 8 design variables define the shape, height, size, availability. A year-long lighting schedule is generated placement of the skylights, the size of clerestories, and and import into energy model for the energy simulation. the shape of the building. The combination of these variables is not found in precedent skylight studies. The The solution space for the design is represented by a design variables are marked in Figure 2 and Figure 3. sample of 1000 design options. The sample is randomly Figure 3 is the enlargement of the southeast corner of the selected from all the possible combinations of all the building. The design variables include building depth, design variables. A Grasshopper plug-in, Octopus is the distance between the skylight and the roof perimeter, used as an engine to generate the 1000 design option and the length of the side of the skylight, the south curb automate the 1000 daylight-energy simulation process. height, the north curb height, the height of south The performance metrics obtained from the simulation clerestory, the height of north clerestory, and the height are Energy Use Intensity (EUI) and Useful Daylight of east and west clerestory. The ranges of the variables Illuminance (UDI). Explanations of the performance are explained in Table 1. The 8 variables are named V1 metrics will be discussed in the simulation output to V8 for short. The range of each variable is divided into section. Finally, based on the building variables data and 10 steps for the simulation. Each variable can vary simulation result, sensitivity analysis is performed to independently, and take any value at the 10 steps. © 2018 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us). 158 For personal use

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