Which factor is essential when designing lighting to meet prescribed illuminance levels?

• A. Target lux levels for the space
• B. Luminaire efficiency
• C. Distribution and glare control
• D. Energy consumption

Answer: (A)

Starting with the target illuminance for the space is essential. The prescribed lux level defines exactly how bright the space needs to be for the tasks performed there. Without specifying this target, you can’t determine how much light is required or what fixtures will be capable of delivering it. Once you know the desired lux, you can calculate the total lumens needed for the area and select luminaires and spacing that provide that amount evenly and comfortably.

The other factors matter for how realistically you meet that target: luminaire efficiency affects how many lumens you must install, distribution and glare control influence how evenly and comfortably the light falls on the work plane, and energy use drives optimization. But none of these determine the required brightness itself—that criterion comes from the target lux level for the space.