CLD Daylighting Design 2 — Questions and Answers
Question 1: Which metric best quantifies the potential for glare from daylighting in a space over an entire year?
- Daylight Glare Probability (DGP)
- Useful Daylight Illuminance (UDI)
- Daylight Glare Index (DGI)
- Annual Glare (AG) using Daylight Availability Profiles (Correct answer)
Correct answer: Annual Glare (AG) using Daylight Availability Profiles
Annual Glare (AG) using Daylight Availability Profiles evaluates glare risk across all occupied hours throughout the year, making it the most comprehensive annual metric.
Question 2: A south-facing clerestory window primarily delivers daylight to which area of a room?
- The perimeter zone near the window wall
- The task surfaces directly below the clerestory
- The deeper interior zones away from the primary façade (Correct answer)
- Only vertical surfaces opposite the clerestory
Correct answer: The deeper interior zones away from the primary façade
Clerestory windows are positioned high on walls to project daylight deep into interior zones that perimeter windows cannot adequately reach.
Question 3: In climate-based daylight modeling (CBDM), which input file provides the annual hourly solar and sky data?
- IES photometric file (.ies)
- EnergyPlus Weather file (.epw) (Correct answer)
- Radiance scene description (.rad)
- LEED Daylight Credit calculator (.xlsx)
Correct answer: EnergyPlus Weather file (.epw)
The EnergyPlus Weather (.epw) file contains 8,760 hours of measured or synthesized climate data including direct normal and diffuse horizontal irradiance used in CBDM.
Question 4: What is the primary daylighting benefit of using a light shelf on a south-facing façade?
- Eliminating all direct solar penetration into the space
- Redirecting high-angle sunlight onto the ceiling to increase depth of penetration (Correct answer)
- Reducing the visible transmittance of the glazing system
- Providing shading only for occupants seated near the window
Correct answer: Redirecting high-angle sunlight onto the ceiling to increase depth of penetration
A light shelf reflects high-angle sunlight upward onto the ceiling, which then bounces it deeper into the room while also shading the lower glazing from direct sun.
Question 5: Useful Daylight Illuminance (UDI) defines the 'useful' range of daylight illuminance as approximately:
- 100–500 lux
- 300–3,000 lux (Correct answer)
- 500–10,000 lux
- 50–300 lux
Correct answer: 300–3,000 lux
UDI defines the useful range as 300–3,000 lux, where values below cause insufficient illuminance and values above risk glare or overheating.
Question 6: Which sky model distributes luminance uniformly across the entire sky dome?
- CIE Standard Overcast Sky (Correct answer)
- CIE Standard Clear Sky
- Perez All-Weather Sky
- Intermediate Sky Model
Correct answer: CIE Standard Overcast Sky
The CIE Standard Overcast Sky assumes uniform luminance across the dome (actually three times brighter at zenith), making it the conservative basis for daylight factor calculations.
Question 7: When designing a daylit atrium, which design strategy most effectively prevents the atrium from becoming a heat trap in summer?
- Maximizing glazed roof area to admit more diffuse light
- Incorporating operable vents or a thermal chimney effect at the top of the atrium (Correct answer)
- Using low-VT tinted glazing on all atrium sides
- Installing high-efficacy electric lighting as a backup system
Correct answer: Incorporating operable vents or a thermal chimney effect at the top of the atrium
Operable vents at the top of an atrium exploit the stack effect (thermal chimney) to exhaust hot air that accumulates at the peak, preventing overheating.
CLD Daylighting Design 2
Which metric best quantifies the potential for glare from daylighting in a space over an entire year?