A Study Of Daylight Modeling Approaches Applied In LEED
Open Access
- Author:
- Esmailian, Maryam
- Graduate Program:
- Architecture
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- August 18, 2021
- Committee Members:
- Ute Poerschke, Program Head/Chair
Ute Poerschke, Thesis Advisor/Co-Advisor
Lisa Domenica Iulo, Thesis Advisor/Co-Advisor
Richard Mistrick, Committee Member - Keywords:
- Daylight
LEED Daylight Credit
Simulation
Shading Devices - Abstract:
- Across various versions of USGBC Leadership in Energy and Environmental Design (LEED), the intent of the Daylight Credit has always been to connect building occupants with the outdoors and reduce the use of electrical lighting by introducing adequate daylight into the space. However, the credit requirements and assessment methods have evolved over time. The most recent version of LEED (v4.1) provides three options for assessing the Daylight Credit. The first two options are based on computer simulation, whereas the third relies on physical measurement. Option 1 performs annual simulation of “Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE).” sDA indicates the sufficiency of daylight inside a room and ASE shows the potential risk of visual discomfort. Option 2 adopts a point-in-time approach, which demonstrates through computer modeling that a sufficient area of a space will have illuminance levels between 300 lux and 3,000 lux at both 9 a.m. and 3 p.m., on a clear-sky day at the equinoxes (15 days within September 21st and March 21st). Option 3 is based on measurement of the illuminance level in the physical space rather than computer simulations. Another major difference among the options is that Option 1 fully adopts the Climate-Based Daylight Modelling (CBDM) approach, predicting hourly daylight quantity on an annual basis, including the application of interior shades when direct sunlight enters the space, while Option 2 and Option 3 measure daylight performance on some days and hours, with no consideration of interior shading. In LEED v4.1 there are some changes in performance thresholds in comparison to LEED v4 such that all options can now provide 3 points maximum. According to USGBC (E-mail interview, 2020) Option 2 is used most often among certified projects. This research focuses on the first two options in order to assess whether their results are in line with each other, and to find out whether a space which contributes to points in one option would also contribute if the other option is applied, given that Option 1 and Option 2 adopt totally different approaches. To this end, an office space model, located on the ground floor of a building with dimensions of 30 feet × 30 feet × 10 feet and a WWR of 40%, was simulated under the conditions of Option 1 and Option 2. The simulations were run in 5 different cities, considering a variety of window orientations and two different interior shading devices as well as with and without an overhang. The findings of this study clearly show that significantly different results can happen between the two simulation approaches for quantifying the percentage of a space that is daylit for the purpose of evaluating LEED credits.