Exam 3 - Lighting

What is Coefficient of Utilization (CU)?

The ratio of light reaching the work plane to the total light produced

What does CU measure?

Efficiency of delivering light to the work plane

If a space has a CU of 70%, what does this mean?

70% of lumens reach the work plane

What factors affect CU?

Room size, surface reflectance, luminaire type

How do wall reflectances impact CU?

Light walls increase CU

How does room size affect CU?

Larger rooms can have higher CU because more light hits the work plane directly

How does luminaire distribution affect CU?

Focused distribution can increase CU

What is Light Loss Factor (LLF)?

Light loss over time due to variuos factors

What are the components of LLF?

LLD, RSDD, LBO

What is Lamp Lumen Depreciation (LLD)?

Decrease in light output as lamp ages

What is Room Surface Dirt Depreciation (RSDD)?

Loss of light due to due to dirty surfaces

What is Lamp Burnout (LBO)?

Lamps failing and no longer producing light

What is Room Cavity Ratio (RCR)?

A ratio describing room proportions

Why is RCR needed?

To find CU from the table

What is cavity height?

Height from luminaire to work plane

How do you calculate cavity height?

Luminaire Height - Work Plane Height

What is the Lumen Method used for?

Calculating average light in a space

What does the Lumen method calculate?

Average footcandles

When is the Lumen Method used?

During design or evaluating existing spaces

What is the Point-by-Point Method used for?

Light at a specific point

What does the Point-by-Point Method calculate?

Illuminance at a specific location

What information is required for Point-by-Point calculations?

Angle, intensity, distance

What is candlepower (I)?

Light intensity in a specific direction

What is the formula for RCR?

RCR = (5)(cavity height)(L+W) / Area

What is the formula for horizontal illuminance?

FC = (I × cosθ) / D²

What is the formula for vertical illuminance?

FC = (I × sinθ) / D²

Lumen Method is also called Zonal Cavity Method. (T or F)

True

What is the formula used to calculate FC?

FC = (Total Lumens)(CU)(LLF) / Area

What formula is used to calculate the number of luminaires?

(Area)(FC) ÷ (Total Lumens per fixture)(CU)(LLF)