CLD Daylighting Design 4 — Questions and Answers
Question 1: A tubular daylighting device (TDD) is most appropriate for which building condition?
- A large open-plan office with a glazed curtain wall
- An interior room with no direct access to an exterior wall or roof (Correct answer)
- A south-facing façade needing seasonal solar control
- A multi-story atrium requiring high-ceiling illumination
Correct answer: An interior room with no direct access to an exterior wall or roof
TDDs (also called sun tubes or tubular skylights) use a reflective tube to transport daylight from a roof-mounted collector to interior rooms that have no direct exterior access.
Question 2: Which exterior shading device is most effective at blocking low-angle morning or afternoon sun on an east or west façade?
- Horizontal overhangs
- Vertical fins (Correct answer)
- Light shelves
- Brise-soleil with horizontal louvers
Correct answer: Vertical fins
Vertical fins are most effective at blocking low-angle horizontal sun from east and west orientations because they intercept solar azimuth angles that horizontal overhangs cannot block.
Question 3: The Daylight Factor (DF) is defined as the ratio of:
- Interior illuminance to exterior horizontal illuminance under a standard overcast sky, expressed as a percentage (Correct answer)
- Peak interior lux to peak exterior lux on a clear sunny day
- Daylight hours to total hours in the year at a given latitude
- Window area to floor area of the daylit zone
Correct answer: Interior illuminance to exterior horizontal illuminance under a standard overcast sky, expressed as a percentage
Daylight Factor is the ratio of interior illuminance at a point to the simultaneous unobstructed exterior horizontal illuminance under a CIE standard overcast sky, expressed as a percentage.
Question 4: When performing a daylight autonomy (DA) simulation, which threshold illuminance is most commonly used as the minimum acceptable level for office tasks?
- 100 lux
- 300 lux (Correct answer)
- 500 lux
- 1,000 lux
Correct answer: 300 lux
300 lux is the standard minimum threshold used in spatial Daylight Autonomy (sDA) calculations, reflecting IES recommended task illuminance for general office work.
Question 5: What is the primary purpose of a 'bird-friendly' frit pattern applied to exterior glazing in a daylighting system?
- To increase visible transmittance by reducing reflectivity
- To break up the visual continuity of glass and reduce bird-strike mortality (Correct answer)
- To improve thermal performance by acting as a shading coefficient modifier
- To provide a diffusing surface that scatters direct sunlight into the interior
Correct answer: To break up the visual continuity of glass and reduce bird-strike mortality
Ceramic frit or dot patterns applied to glazing interrupt the visual 'invisibility' of glass to birds, reducing fatal collisions while still admitting daylight.
Question 6: In a perimeter daylighting zone, occupancy-based dimming controls for electric lighting are most effective when luminaires are zoned:
- In a single zone for the entire floor plate
- In rows parallel to the window wall, each on an independent circuit (Correct answer)
- In rows perpendicular to the window wall, each on an independent circuit
- By occupant workstation, each on a personal dimming switch
Correct answer: In rows parallel to the window wall, each on an independent circuit
Zoning luminaires in rows parallel to the window wall allows photosensors to dim each row independently based on the gradient of daylight that decreases with distance from the window.
Question 7: Which building type typically has the highest potential for daylighting to offset electric lighting energy use due to its occupancy schedule?
- 24-hour hospital patient wards
- Residential apartments
- Office buildings with standard 8 AM–6 PM occupancy (Correct answer)
- Underground parking structures
Correct answer: Office buildings with standard 8 AM–6 PM occupancy
Office buildings with daytime-only occupancy have the highest overlap between occupancy hours and available daylight hours, maximizing the energy offset potential of daylighting controls.
CLD Daylighting Design 4
A tubular daylighting device (TDD) is most appropriate for which building condition?