CLD Sustainability 3 — Questions and Answers
Question 1: What does the term 'embodied carbon' refer to in the context of sustainable lighting design?
- CO₂ emitted during building operation from lighting electricity use
- Greenhouse gas emissions from manufacturing, transporting, and disposing of lighting products (Correct answer)
- The carbon offset credits purchased to neutralize a project's footprint
- CO₂ absorbed by building materials over their lifespan
Correct answer: Greenhouse gas emissions from manufacturing, transporting, and disposing of lighting products
Embodied carbon encompasses lifecycle emissions from raw material extraction, product manufacturing, transportation, installation, and end-of-life disposal of lighting equipment.
Question 2: A designer is comparing two LED luminaires with identical lm/W. Luminaire A has a longer rated life. Why is this the more sustainable choice?
- Longer life reduces relamping labor and material waste from fewer replacements (Correct answer)
- Longer-life luminaires always have higher CRI
- They generate less heat, improving HVAC efficiency
- Extended life warranties reduce embodied carbon during manufacturing
Correct answer: Longer life reduces relamping labor and material waste from fewer replacements
A longer-rated life reduces the frequency of lamp and luminaire replacements, lowering labor costs, material consumption, and landfill waste over the project lifespan.
Question 3: Which circadian lighting principle is most relevant to sustainable human-centric design?
- Using high-CCT (5000K+) light at night to boost alertness
- Providing higher correlated color temperature and intensity in the morning to support natural wake cycles (Correct answer)
- Maintaining constant 3000K light throughout the day for consistency
- Maximizing blue-wavelength emission at all hours to suppress melatonin
Correct answer: Providing higher correlated color temperature and intensity in the morning to support natural wake cycles
Aligning cooler, brighter light in the morning with natural dawn conditions supports circadian rhythms, improving occupant health and well-being without increasing total energy use.
Question 4: In ASHRAE 90.1, what is the primary compliance pathway for interior lighting energy in a commercial building?
- Climate zone compliance
- Lighting Power Density (LPD) limits (Correct answer)
- Daylight autonomy targets
- Luminous efficacy minimums
Correct answer: Lighting Power Density (LPD) limits
ASHRAE 90.1 sets maximum Lighting Power Density (W/ft²) limits by space type or building type as the primary compliance metric for interior lighting.
Question 5: A sports venue lighting project seeks to minimize light trespass onto adjacent residential areas. Which luminaire characteristic is most critical?
- High efficacy (lm/W)
- Full-cutoff or sharp-cutoff optical control (Correct answer)
- High color rendering index (CRI ≥ 90)
- Wide beam angle for broad coverage
Correct answer: Full-cutoff or sharp-cutoff optical control
Full-cutoff or sharp-cutoff optics direct light precisely where needed and prevent spill onto adjacent properties, directly reducing trespass and sky glow.
Question 6: Which protocol allows lighting systems to communicate energy data to building management systems for sustainability monitoring?
- DALI-2
- BACnet (Correct answer)
- DMX512
- 0–10V dimming
Correct answer: BACnet
BACnet is an open communication protocol widely used to integrate lighting, HVAC, and other building systems with building management systems (BMS) for energy monitoring and control.
Question 7: What is 'spatial daylight autonomy' (sDA) as used in sustainable lighting metrics?
- The percentage of floor area that meets a minimum illuminance threshold from daylight alone for a specified percentage of occupied hours (Correct answer)
- The ratio of daylight to electric light in a given space
- The number of hours per year a space receives direct sunlight
- The maximum daylight factor achievable at a window
Correct answer: The percentage of floor area that meets a minimum illuminance threshold from daylight alone for a specified percentage of occupied hours
sDA measures the percentage of floor area that achieves at least 300 lux from daylight for at least 50% of occupied hours annually, as defined by IES LM-83.
CLD Sustainability 3
What does the term 'embodied carbon' refer to in the context of sustainable lighting design?