Which two factors are essential to determine lighting requirements?

• A. Target illuminance level and space area
• B. Number of occupants and outlet count
• C. Room color and wall texture
• D. Fixture warranty and brand

Answer: (A)

Determining lighting requirements starts with how bright the space needs to be and how large the space is. The target illuminance level tells you the desired light intensity on working surfaces, usually given in lux (or foot-candles), based on what the space is used for. The space area tells you how much surface area needs to be lit. Multiply the target illuminance by the area to get the total amount of light the fixtures must deliver, expressed in lumens. From there you select fixtures that can provide that lumens output while accounting for how effectively light is distributed, how much is lost over time, and how walls and surfaces reflect light.

The other factors shown don’t set the basic lighting requirement. The number of occupants and outlet count doesn’t determine the required brightness. Room color and wall texture affect how bright a space feels and how light is reflected, but they don’t establish the needed lumens. Fixture warranty and brand don’t influence the amount of light required.