Lighting Calculations & Software Flashcards

In an exterior lighting calculation, the concept of 'maintained horizontal illuminance' vs. 'initial horizontal illuminance' differ because:

Answer: Maintained values apply light loss factors to account for real-world degradation over time

Maintained illuminance = initial illuminance × LLF, accounting for lamp lumen depreciation, luminaire dirt, and other losses over the maintenance cycle.

In AGi32, the 'Radiosity' calculation method is preferred over direct illuminance calculation when:

Answer: Interreflections between surfaces significantly contribute to overall illuminance

Radiosity accounts for light bouncing between surfaces, making it accurate for spaces where interreflections (indirect light) substantially contribute to illuminance levels.

What is the maximum-to-minimum illuminance uniformity ratio recommended by IES RP-1 for typical office tasks?

Answer: 3:1 maximum to minimum

IES RP-1 for office lighting recommends that the maximum-to-minimum illuminance ratio not exceed 3:1 to avoid visual discomfort from excessive variation.

A photometric report shows vertical illuminance (Ev) values. This metric is most important for evaluating:

Answer: Facial visibility, security camera performance, and display legibility

Vertical illuminance is critical for facial recognition in security applications, camera performance, and the readability of vertically oriented displays and signage.

Which metric best describes the energy performance of a complete daylighting plus electric lighting system over an annual period?

Answer: Annual Lighting Energy Numeric Indicator (LENI) in kWh/m²/year

LENI (kWh/m²/year) captures annual energy consumption including dimming from daylight harvesting, occupancy controls, and seasonal variation.

In photometric software, setting the 'ground reflectance' value to 0.20 rather than 0.10 in an exterior parking lot simulation will:

Answer: Increase calculated illuminance values due to more interreflected light from the ground

A higher ground reflectance means more light bounces back upward, contributing to overall illuminance levels especially on vertical surfaces and in adjacent areas.

A lighting consultant is modeling a museum gallery and needs to limit UV radiation exposure to 75 μW/lm. Which software feature helps verify compliance?

Answer: Spectral power distribution (SPD) analysis combined with luminaire UV output data

UV compliance in conservation lighting requires combining the SPD of each source with its luminous output to verify that the UV per lumen ratio stays within preservation limits.