CLD Sustainable & Energy-Efficient Lighting Solutions 2

Question 1

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

Accepted Answer

Daylight harvesting combined with occupancy sensing

Answer

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

Question 2

What does the term 'luminous efficacy' measure?

Accepted Answer

Lumens output per watt of electrical power consumed

Answer

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

Question 3

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

Accepted Answer

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

Answer

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

Question 4

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

Accepted Answer

ASHRAE 90.1

Answer

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

Question 5

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

Accepted Answer

More lumens delivered to the task with less lamp wattage

Answer

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

(CLD) Certified Lighting Designer Practice Test