CLD Sustainable & Energy-Efficient Lighting Solutions 5 — Questions and Answers
Question 1: Which of the following best describes the 'whole building' method versus the 'space-by-space' method in ASHRAE 90.1 lighting compliance?
- Whole building averages LPD across the entire building; space-by-space applies individual limits per room type (Correct answer)
- Whole building requires daylight controls; space-by-space exempts spaces under 100 sf
- Whole building uses watts per linear foot; space-by-space uses watts per square foot
- They are equivalent methods yielding identical allowances for any given building
Correct answer: Whole building averages LPD across the entire building; space-by-space applies individual limits per room type
The whole-building method applies a single averaged W/ft² budget to the total floor area, while space-by-space assigns specific LPD limits to each space type, allowing design flexibility.
Question 2: A CLD is designing a parking garage with a target of reducing energy use by 60% versus a conventional HID system. Which combination of strategies is most likely to achieve this?
- LED fixtures + occupancy-based bi-level control + daylight harvesting at perimeter (Correct answer)
- LED fixtures alone with no controls
- T5HO fluorescent fixtures + timer-based control
- Induction lamps + manual switching
Correct answer: LED fixtures + occupancy-based bi-level control + daylight harvesting at perimeter
Combining LED efficacy gains (~50% savings vs. HID), bi-level occupancy dimming, and perimeter daylight harvesting compounds savings to reach 60% or more in parking structures.
Question 3: What is 'circadian-effective' lighting design primarily concerned with in sustainable buildings?
- Minimizing blue-channel output at all times to reduce energy waste
- Aligning the spectrum and intensity of light with occupants' natural biological rhythms to support health (Correct answer)
- Maximizing color rendering for accurate visual task performance
- Reducing flicker to below 1% at all dimming levels
Correct answer: Aligning the spectrum and intensity of light with occupants' natural biological rhythms to support health
Circadian-effective lighting uses spectrally tunable or well-designed fixed-spectrum sources to support alertness during the day and promote relaxation and melatonin production in the evening.
Question 4: In an energy audit of an existing office building, which existing condition most strongly indicates an opportunity for lighting energy savings?
- Illuminance levels consistently 3× the IES recommended target with no dimming controls (Correct answer)
- Presence of T8 lamps installed within the last two years
- Fixtures equipped with occupancy sensors but no daylight sensors
- Use of 3000K CCT in task areas
Correct answer: Illuminance levels consistently 3× the IES recommended target with no dimming controls
Chronic overlighting (illuminance far exceeding IES targets) with no dimming controls represents direct wasted energy that can be recovered by reducing wattage or adding controls.
Question 5: What role does a 'lighting energy dashboard' or submetering system play in a sustainable building's post-occupancy phase?
- It controls luminaire color temperature based on occupant mood inputs
- It provides real-time and historical energy data to verify savings and identify control system failures (Correct answer)
- It replaces the need for a commissioning agent after installation
- It automatically adjusts LPD calculations to reflect seasonal changes
Correct answer: It provides real-time and historical energy data to verify savings and identify control system failures
Submetering and dashboards enable ongoing measurement and verification (M&V), confirming that projected savings are achieved and flagging malfunctioning sensors or drivers.
Question 6: Which IES document establishes recommended illuminance levels used as the basis for energy-code LPD allowances?
- IES LM-79 (Electrical and Photometric Measurements of SSL Products)
- IES TM-15 (Luminaire Classification System for Outdoor Luminaires)
- IES RP-1 (Recommended Practice for Office Lighting) and other application RPs (Correct answer)
- IES TM-21 (Projecting Long-Term Luminaire Lumen Maintenance)
Correct answer: IES RP-1 (Recommended Practice for Office Lighting) and other application RPs
IES Recommended Practices (RP series) define illuminance targets per application type, which inform ASHRAE 90.1's space-by-space LPD allowances.
Question 7: When a lighting designer applies 'right-sizing' to a sustainable retrofit, the primary goal is to:
- Install the highest-efficacy fixture available regardless of delivered illuminance
- Match the installed lumen output and distribution precisely to the actual task requirements, avoiding over- or under-lighting (Correct answer)
- Replace all existing fixtures with the same wattage LED equivalents to simplify budgeting
- Maximize lamp quantity to provide lighting redundancy if individual sources fail
Correct answer: Match the installed lumen output and distribution precisely to the actual task requirements, avoiding over- or under-lighting
Right-sizing delivers exactly the illuminance recommended by IES for each task, avoiding the energy waste of overlighting while ensuring visual adequacy.
CLD Sustainable & Energy-Efficient Lighting Solutions 5
Which of the following best describes the 'whole building' method versus the 'space-by-space' method in ASHRAE 90.1 lighting compliance?