CLD Sustainable & Energy-Efficient Lighting Solutions 3 — Questions and Answers
Question 1: Under LEED v4.1, which credit category directly rewards reductions in exterior lighting power and control of uplight?
- Sustainable Sites: Light Pollution Reduction (Correct answer)
- Energy & Atmosphere: Optimize Energy Performance
- Indoor Environmental Quality: Interior Lighting
- Materials & Resources: Building Product Disclosure
Correct answer: Sustainable Sites: Light Pollution Reduction
LEED v4.1 Sustainable Sites credit 'Light Pollution Reduction' awards points for meeting uplight, backlight, and glare limits using the BUG rating method.
Question 2: What is the key difference between 'connected load' and 'demand load' when calculating lighting energy use?
- Connected load is DC power; demand load is AC power
- Connected load is the sum of all installed fixture wattages; demand load accounts for controls reducing average power draw (Correct answer)
- Connected load applies only to emergency circuits; demand load applies to normal circuits
- They are interchangeable terms in ASHRAE 90.1
Correct answer: Connected load is the sum of all installed fixture wattages; demand load accounts for controls reducing average power draw
Connected load is the total installed wattage, while demand load reflects actual average consumption after controls (dimming, occupancy) reduce operating levels.
Question 3: A hospital corridor is lit to 30 fc for normal operation and automatically steps down to 5 fc when unoccupied at night. This strategy is best described as:
- Tunable white lighting
- Bi-level switching (Correct answer)
- Circadian stimulus adjustment
- Lumen depreciation compensation
Correct answer: Bi-level switching
Bi-level switching (or stepped dimming) uses occupancy sensors to reduce light levels to a standby level rather than switching fully off, balancing safety with energy savings.
Question 4: Which lamp type is prohibited by US DOE regulations phased in from August 2023 due to its inefficiency?
- Compact fluorescent lamps (CFLs)
- General service incandescent and halogen lamps below 45 lm/W (Correct answer)
- T8 linear fluorescent lamps
- Metal halide lamps below 100W
Correct answer: General service incandescent and halogen lamps below 45 lm/W
The DOE's 2023 ruling effectively banned general service lamps that do not meet a 45 lm/W minimum efficacy, eliminating most incandescent and halogen A-lamps.
Question 5: In a daylight harvesting system, 'closed-loop' control differs from 'open-loop' control because it:
- Uses a photosensor facing the window to measure incoming daylight only
- Measures actual workplane illuminance and adjusts electric light to maintain a setpoint (Correct answer)
- Relies on astronomical time clocks rather than photosensors
- Controls only the fixtures nearest to the perimeter glazing
Correct answer: Measures actual workplane illuminance and adjusts electric light to maintain a setpoint
Closed-loop systems use a photosensor aimed at the task plane to measure combined daylight and electric light, continuously adjusting output to hit a target illuminance level.
Question 6: What is the primary sustainability advantage of using solid-state lighting (SSL) over high-intensity discharge (HID) sources in exterior applications?
- SSL produces a warmer color temperature preferred in residential zones
- SSL eliminates the restrike delay and contains no mercury, while typically achieving higher efficacy (Correct answer)
- SSL fixtures have lower upfront cost than HID luminaires
- SSL is immune to thermal lumen depreciation in cold climates
Correct answer: SSL eliminates the restrike delay and contains no mercury, while typically achieving higher efficacy
LED-based SSL has no restrike delay (important for safety), contains no mercury (reducing hazardous waste), and modern products exceed HID efficacy in most applications.
Question 7: A Life Cycle Cost (LCC) analysis for a lighting project should include all of the following EXCEPT:
- Initial fixture and installation costs
- Annual energy costs over the analysis period
- Lamp and maintenance replacement costs
- The aesthetic design fee paid to the architect (Correct answer)
Correct answer: The aesthetic design fee paid to the architect
LCC captures hardware, installation, energy, and maintenance costs over a system's life; design fees are a project cost but are not part of the lighting system's operational life cycle.
CLD Sustainable & Energy-Efficient Lighting Solutions 3
Under LEED v4.1, which credit category directly rewards reductions in exterior lighting power and control of uplight?