CLC Daylighting Integration 2 — Questions and Answers
Question 1: What is the primary purpose of a light shelf in daylighting design?
- To block all direct sunlight from entering a space
- To reflect sunlight deeper into a room while shading the lower window zone (Correct answer)
- To diffuse electric light from ceiling fixtures
- To measure illuminance levels near the perimeter
Correct answer: To reflect sunlight deeper into a room while shading the lower window zone
A light shelf reflects sunlight onto the ceiling and deeper into the space while the shelf itself shades the lower portion of the window, reducing glare.
Question 2: Which metric best quantifies the availability of daylight in a space over an entire year?
- Daylight Factor (DF)
- Useful Daylight Illuminance (UDI)
- Climate-Based Daylight Modeling (CBDM) (Correct answer)
- Annual Sunlight Exposure (ASE)
Correct answer: Climate-Based Daylight Modeling (CBDM)
Climate-Based Daylight Modeling (CBDM) uses actual hourly weather data to simulate annual daylight availability, providing a more realistic picture than static metrics.
Question 3: A south-facing clerestory in the Northern Hemisphere is most effective at admitting daylight during which season?
- Summer, when the sun is highest
- Winter, when the sun is lowest and shines directly through (Correct answer)
- Spring and fall equally
- It performs equally in all seasons
Correct answer: Winter, when the sun is lowest and shines directly through
South-facing clerestories in the Northern Hemisphere receive the most direct sunlight in winter when the sun's altitude is low, making them most effective then.
Question 4: What does an Daylight Autonomy (DA) value of 65% indicate for a given sensor point?
- 65% of the floor area receives adequate daylight
- The target illuminance is met by daylight alone for 65% of annual occupied hours (Correct answer)
- 65% of the daylight comes from diffuse sky rather than direct sun
- The space uses 65% less electric energy due to daylighting
Correct answer: The target illuminance is met by daylight alone for 65% of annual occupied hours
Daylight Autonomy (DA) is the percentage of occupied hours during a year when a target illuminance threshold is met solely by daylight at a specific point.
Question 5: Which glazing characteristic most directly reduces solar heat gain while still allowing visible light transmission?
- High U-value
- Low Light-to-Solar Gain (LSG) ratio
- High Light-to-Solar Gain (LSG) ratio (Correct answer)
- Low visible light transmittance (VT)
Correct answer: High Light-to-Solar Gain (LSG) ratio
A high LSG ratio means the glazing transmits a greater proportion of visible light relative to total solar heat gain, improving daylighting while controlling heat.
Question 6: In daylighting design, 'borrowed light' refers to:
- Light reflected off neighboring buildings into the subject building
- Daylight transferred from a perimeter zone to an interior zone through interior glazing or openings (Correct answer)
- Supplemental electric light used to fill daylight shortfalls
- Light redirected by external louvers onto an adjacent facade
Correct answer: Daylight transferred from a perimeter zone to an interior zone through interior glazing or openings
Borrowed light is daylight that passes from a daylit perimeter zone into an interior zone via interior windows, sidelights, or clerestories within the building.
Question 7: The CIE overcast sky model assumes luminance is distributed how across the sky dome?
- Uniform across the entire hemisphere
- Brightest at the horizon, darkest at the zenith
- Brightest at the zenith, with luminance decreasing toward the horizon by a factor of about 3 (Correct answer)
- Concentrated in a bright solar disk with uniform diffuse surround
Correct answer: Brightest at the zenith, with luminance decreasing toward the horizon by a factor of about 3
The CIE Standard Overcast Sky has a zenith that is approximately three times brighter than the horizon, creating a gradient used in Daylight Factor calculations.
CLC Daylighting Integration 2
What is the primary purpose of a light shelf in daylighting design?