CLD Sustainability 2 — Questions and Answers
Question 1: Which lighting control strategy saves the most energy by reducing output when daylight is available?
- Occupancy sensing
- Daylight harvesting (daylight dimming) (Correct answer)
- Scheduled time switching
- Manual dimming
Correct answer: Daylight harvesting (daylight dimming)
Daylight harvesting automatically dims or switches off electric lighting in response to available natural light, directly offsetting electric energy use.
Question 2: A lighting designer specifies luminaires with a Unified Glare Rating (UGR) below 19. What sustainability co-benefit does this primarily provide?
- Reduced lamp replacement frequency
- Improved occupant visual comfort and productivity (Correct answer)
- Lower lumen maintenance factor
- Decreased transformer losses
Correct answer: Improved occupant visual comfort and productivity
Low UGR reduces glare-induced visual discomfort, supporting occupant well-being and productivity, a key human-centric sustainability outcome.
Question 3: Under LEED v4.1, which credit category specifically addresses light pollution reduction through exterior lighting control?
- Indoor Environmental Quality – Daylight
- Sustainable Sites – Light Pollution Reduction (Correct answer)
- Energy & Atmosphere – Optimize Energy Performance
- Materials & Resources – Building Life-Cycle Impact
Correct answer: Sustainable Sites – Light Pollution Reduction
LEED v4.1 Sustainable Sites credit 'Light Pollution Reduction' requires shielding and limiting uplight and trespass from exterior luminaires.
Question 4: A project targets net-zero energy. What is the correct order of the energy hierarchy a designer should follow?
- Generate, reduce, optimize
- Reduce, optimize, generate (Correct answer)
- Optimize, generate, reduce
- Generate, optimize, reduce
Correct answer: Reduce, optimize, generate
Best practice is to first reduce demand through efficiency, then optimize controls and systems, and finally generate on-site renewable energy to offset remaining loads.
Question 5: Which metric best quantifies the visual efficacy of a luminaire for a sustainable design comparison?
- Watts per circuit
- Luminous efficacy (lm/W) (Correct answer)
- Color Rendering Index (CRI)
- Beam angle in degrees
Correct answer: Luminous efficacy (lm/W)
Luminous efficacy (lm/W) measures how efficiently a luminaire converts electrical power to visible light, making it the primary metric for sustainable comparisons.
Question 6: A parking lot retrofit replaces 175W metal halide with 60W LED luminaires. What is the approximate percentage energy reduction?
- About 25%
- About 35%
- About 66% (Correct answer)
- About 85%
Correct answer: About 66%
Replacing 175W with 60W yields a reduction of 115W, which is approximately 66% of the original 175W consumption.
Question 7: Which IES standard provides guidelines for energy-efficient exterior roadway and area lighting?
- IES TM-15
- IES RP-8 (Correct answer)
- IES RP-28
- IES TM-21
Correct answer: IES RP-8
IES RP-8 (Recommended Practice for Design and Maintenance of Roadway and Parking Facility Lighting) provides illuminance and energy guidance for exterior roadway lighting.
CLD Sustainability 2
Which lighting control strategy saves the most energy by reducing output when daylight is available?