CLD Lighting Design Principles & Techniques 5

Question 1

What is the function of an 'emergency egress lighting' system, and what minimum illuminance does NFPA 101 require at floor level?

Accepted Answer

Illuminates exit paths during power failure; requires a minimum of 1 fc (10.8 lux) average at floor level

Answer

NFPA 101 (Life Safety Code) mandates emergency egress lighting to activate within 10 seconds of normal power failure and maintain at least 1 fc (10.8 lux) average along the means of egress at floor level.

Question 2

What is 'visual comfort probability' (VCP) and how does it relate to unified glare rating (UGR)?

Accepted Answer

VCP is an older North American metric predicting the percentage of observers finding a system comfortable; UGR is the current international metric for glare assessment

Answer

VCP was developed in North America to express glare comfort as a percentage of satisfied observers, while UGR is the ISO/CIE metric now widely used internationally for interior glare evaluation.

Question 3

A client requests 'human-centric lighting' (HCL) in a corporate headquarters. What biological mechanism does HCL primarily target?

Accepted Answer

Intrinsically photosensitive retinal ganglion cells (ipRGCs) that regulate circadian rhythm via melanopsin

Answer

HCL targets ipRGCs containing melanopsin, which are most sensitive to short-wavelength (blue) light and drive circadian entrainment, alertness, and sleep-wake cycles.

Question 4

When performing a luminaire maintenance factor (LMF) calculation, which four components are typically multiplied together?

Accepted Answer

Lamp lumen depreciation (LLD) × luminaire dirt depreciation (LDD) × room surface dirt depreciation (RSDD) × lamp survival factor (LSF)

Answer

The light loss factor (LLF) or maintenance factor combines LLD, LDD, RSDD, and LSF to predict how illuminance will decrease over the maintenance interval.

Question 5

In exterior façade lighting design, what is the primary reason to avoid aiming floodlights at steep upward angles toward upper stories?

Accepted Answer

They produce wasted uplight, contributing to skyglow and light pollution while potentially violating dark-sky ordinances

Answer

Light aimed steeply upward escapes above the building, contributing to skyglow and light pollution; dark-sky standards (IDA, LEED) limit uplight ratios for exterior installations.

(CLD) Certified Lighting Designer Practice Test

(CLD) Certified Lighting Designer Practice Test

CLD Lighting Design Principles & Techniques 5