CLC Energy Efficiency & Sustainability 3 — Questions and Answers
Question 1: In daylighting design, what is the primary purpose of a light shelf?
- To block glare at the workplane
- To reflect daylight deeper into the building interior (Correct answer)
- To reduce solar heat gain in summer only
- To mount exterior luminaires at window height
Correct answer: To reflect daylight deeper into the building interior
A light shelf is a horizontal reflective surface that bounces daylight off the ceiling to illuminate areas farther from the window.
Question 2: Which metric is used to measure the potential of a building's daylit zones relative to all occupied hours with sufficient daylight?
- Useful Daylight Illuminance (UDI)
- Daylight Autonomy (DA) (Correct answer)
- Climate-Based Daylight Modeling (CBDM)
- Solar Heat Gain Coefficient (SHGC)
Correct answer: Daylight Autonomy (DA)
Daylight Autonomy (DA) expresses the percentage of occupied hours when a point receives at least the target illuminance from daylight alone.
Question 3: A LED lamp has a rated life of 50,000 hours. Operating 12 hours per day, approximately how many years will it last?
- 7 years
- 9 years
- 11 years (Correct answer)
- 14 years
Correct answer: 11 years
50,000 hours ÷ (12 hrs/day × 365 days/year) ≈ 11.4 years.
Question 4: What is the primary environmental benefit of reducing lighting energy consumption in a building connected to a coal-heavy electrical grid?
- Lower noise pollution
- Reduced CO₂ emissions from power generation (Correct answer)
- Decreased water table depletion
- Reduced ozone layer depletion
Correct answer: Reduced CO₂ emissions from power generation
Coal power plants emit significant CO₂; reducing electricity demand directly lowers greenhouse gas emissions at the generation source.
Question 5: Which type of dimming control maintains constant light output over a lamp's life by increasing power as lumens depreciate?
- Daylight dimming
- Lumen maintenance dimming (Correct answer)
- Occupancy-based dimming
- Personal tuning
Correct answer: Lumen maintenance dimming
Lumen maintenance dimming starts fixtures at reduced output and increases drive current over time to compensate for lumen depreciation, saving energy early in lamp life.
Question 6: A 10,000 sq ft office has an allowable LPD of 0.82 W/ft² per ASHRAE 90.1. What is the maximum installed lighting wattage?
- 6,200W
- 8,200W (Correct answer)
- 10,200W
- 12,000W
Correct answer: 8,200W
Maximum wattage = 10,000 ft² × 0.82 W/ft² = 8,200W.
Question 7: Which lighting system characteristic most directly contributes to reducing cooling energy loads in a building?
- High color rendering index (CRI)
- High luminaire efficacy reducing heat output (Correct answer)
- Narrow beam distribution
- High correlated color temperature (CCT)
Correct answer: High luminaire efficacy reducing heat output
More efficacious luminaires waste less energy as heat, reducing the thermal load that HVAC systems must remove.
CLC Energy Efficiency & Sustainability 3
In daylighting design, what is the primary purpose of a light shelf?