Lighting Design Flashcards

What is the primary function of a photosensor (daylight sensor) in a lighting control system?

Answer: Dim or switch off artificial lights in response to available natural daylight

Photosensors measure ambient light levels and automatically dim or switch off electric lights when sufficient daylight is available, reducing energy use through daylight harvesting.

Per NFPA 101 (Life Safety Code), emergency egress lighting must remain operational for a minimum of how long after a power failure?

Answer: 1.5 hours

NFPA 101 requires emergency egress lighting to provide a minimum of 1.5 hours of illumination at required levels following loss of normal power.

In LEED certification, which lighting strategy is most directly credited under the Indoor Environmental Quality (IEQ) category?

Answer: Providing individual occupant lighting controls for adjustability

LEED IEQ credits providing individual occupant lighting controls because personal control over lighting levels improves comfort and occupant satisfaction.

What does DALI stand for in lighting control systems, and what is its key advantage?

Answer: Digital Addressable Lighting Interface — allows individual fixture control

DALI (Digital Addressable Lighting Interface) is a standard protocol that allows each luminaire on a network to be individually addressed and controlled, enabling flexible scene and zone management.

The Light Loss Factor (LLF) is used in lighting calculations to account for:

Answer: The reduction in light output over time due to lamp aging, dirt accumulation, and other factors

The LLF accounts for predictable decreases in maintained illuminance over time, including lamp lumen depreciation, luminaire dirt depreciation, and other maintenance-related factors.

Which lighting control strategy dims electric lights to a predetermined level based on the space's actual usage needs, rather than maximum design levels?

Answer: Task tuning

Task tuning (or institutional tuning) permanently sets the maximum light output of fixtures to match the actual illuminance needs of a space, reducing energy waste from over-lit areas.

Which term describes the phenomenon where a light source causes visual fatigue by flickering at a frequency that may not be consciously perceived?

Answer: Flicker

Flicker refers to rapid, repetitive variation in light output that can cause eyestrain, headaches, and in sensitive individuals may trigger photosensitive responses, even when not consciously noticed.