The Effect of Daylighting Utilization for Different Building Envelope Design on HVAC and Lighting Energy
Date Issued
2015
Date
2015
Author(s)
Fu, Chun
Abstract
In Taiwan, which is in the subtropical area in Asia, there is much intensive beam radiation among whole year, and the hot season is longer than cold one. To resolve the problem of indoor high temperature, a large amount of HVAC energy needs to be consumed. Thus, some common strategies for building envelope design are exterior shading device, reducing the WWR (Window to Wall Ratio), or changing the glazing types. By blocking or reducing part of the radiation heat from outdoors, it helps to save more HVAC energy consumption. However, those strategies also hinders some daylight from entering into the room, therefore increasing additional artificial lighting to compensate for the lack of lights. So, lighting energy increases, and the heat gain from the lighting system also causes additional cooling energy. In addition to consideration of building energy, visual comfort in indoor environment needs to be considered as well. Previous studies have pointed out that visual comfort have positive impact on both work and learning efficiency. A well designed building envelope can both enhance visual comfort and avoid the discomfort caused by excessive daylight. So, the impact of different building envelope designs on both building energy and visual comfort are conducted in this study. In order to deeply understand influence of different building envelope design, this study investigated several factors, such as room shapes, shading device designs, glazing types, and so on. Through daylighting simulation tool (DAYSIM) and building energy simulation tool (EnergyPlus), totally 1458 office cases with different envelope designs are simulated. Then, the simulation results were analyzed through ANOVA (Analysis of variance) and discussed so as to find out influence of each factor and some optimal building envelope designs. Since building energy could not be compared with visual comfort directly, it’s hard to find the best one among all cases. Hence, according to a formula from a citation, which can convert Indoor Environment Quality (IEQ) index into human productivity, in order to evaluate and compare each case on an economic basis. The simulation results shows that visual comfort is positively correlated with energy saving benefits. If UDI (Useful Daylight Index) is enhanced, the energy-saving benefits from less lighting demand and decreased HVAC energy due to less heat gain from lighting device will be significant. Among all factors of building envelope design, room shape, WWR, and glazing types are the most influential. However, sometimes there are compromise between building energy and visual comfort in these factors. For example, WWR of 40% has a mean effect of 1.7 kwh/m2.a, which is compared to the total average of performance, but it also has negative impact of -1.4% on UDI(300-2000). As a result, it’s necessary to carefully pick proper level of the factor. Among the three room shapes, the wider one has the best visual comfort and energy-saving benefit. Because it’s easier to utilize the daylight and improves the quality of indoor daylight, more building energy could be saved. If compared to baseline, which is set as light-on during workhour and WWR of 80%, UDI(300-2000) could be improved by 33.4%, and UDI(>2000) could be reduced by 62.6%. In terms of building energy, it could be reduced by totally 56.9% (33.8% for HVAC energy, and 23.0% for lighting energy).
Subjects
daylight utilization
visual comfort
building energy simulation
daylighting environment simulation
building envelope design
SDGs
Type
thesis
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ntu-104-R02622002-1.pdf
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