Sustainable & Energy-Efficient Lighting Solutions Flashcards

Which lighting control strategy delivers the greatest energy savings in open-plan offices with variable occupancy?

Answer: Daylight harvesting combined with occupancy sensing

Combining daylight harvesting with occupancy sensing addresses both unoccupied periods and available natural light, maximizing energy reduction.

What does the term 'luminous efficacy' measure?

Answer: Lumens output per watt of electrical power consumed

Luminous efficacy is expressed in lumens per watt (lm/W) and quantifies how efficiently a light source converts electrical energy into visible light.

A CLD specifies LED luminaires with an L70 rating of 50,000 hours. What does this mean?

Answer: Lumen output will drop to 70% of initial output at 50,000 hours

L70 is an industry-standard LED lumen maintenance metric indicating the point at which output depreciates to 70% of rated initial lumens.

Which standard provides the primary energy use intensity (EUI) benchmarks for commercial lighting in US buildings?

Answer: ASHRAE 90.1

ASHRAE 90.1 sets mandatory lighting power density (LPD) limits and controls requirements for commercial buildings in the US.

In the context of sustainable design, what is the primary benefit of specifying fixtures with a high Optical System Efficiency (OSE)?

Answer: More lumens delivered to the task with less lamp wattage

High OSE means the optic wastes fewer lumens, so a lower-wattage source can meet the same illuminance target, reducing energy consumption.

A lighting designer is evaluating two LED products: Product A is 130 lm/W and Product B is 110 lm/W. Both meet the photometric requirement. Which factor should most influence the sustainable choice?

Answer: Product B if it carries a longer warranty and better lumen maintenance data

A longer warranty and verified lumen maintenance (L70/L80 data) indicate real-world energy and replacement savings that can outweigh a modest efficacy gap.

Which metric is used to quantify the light pollution impact of an outdoor luminaire on the night sky?

Answer: Backlight-Uplight-Glare (BUG) rating

The BUG rating classifies a luminaire's backlight, uplight, and glare distribution, with uplight being the component most directly linked to sky glow.