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factored into the formula. Group re-lamping is always cost effective over spot re-
lamping. Lamps that are reliable and need replacement every several years (versus
months) need to be specified. In addition, specify compatible equipment. For example,
when lighting is controlled with occupancy sensors, the ballast and lamp need to
respond to this type of frequent control. Lamps that work well with occupancy sensors
are rapid start and programmed start fluorescent and induction lamps. Instant start
fluorescent and HID lamps are not compatible with occupancy sensors.
Energy Models: Even though energy efficient lighting reduces the building
operating energy use, lower lighting energy also decreases HVAC loads. Decreased
HVAC loads can represent initial cost savings. Energy models should be performed for
each building to estimate the impact of daylighting, building envelope design, energy
efficient electric lighting, lighting controls, HVAC loads and controls. These models will
best inform the designers on system wide decisions and the life cycle cost impacts.
Federal economic analysis: Refer to FEMP Economics for Energy Effective
Lighting for Offices for life cycle cost analysis examples. Lighting system options have
been calculated for open and small offices showing energy usage, illuminance levels,
quality visual design factors, initial costs per square foot, annual operating costs per
square foot, simple payback in years and Federal Savings to Investment Ratios.
IESNA economic analysis: Chapter 25 "Lighting Economics" in the Lighting
Handbook states multiple cost comparison methods. The Cost of Light calculates the
unit cost of light per lamp using lamp efficacy, energy and replacement costs. Two
other cost comparisons are explained including the Simple Rate of Return and more
robust Life-Cycle Cost-Benefit Analysis.
LUMINAIRES. Luminaires are comprised of a light source (or lamp),
reflector, shade, lens, refractor, mounting hardware and an electrical connection.
Fluorescent and high intensity discharge luminaires include a ballast to operate the
buildings and 5% of the total energy consumption in the United States2, it is important to
use energy efficient equipment.
Pendant Mounted Luminaires. Pendant mounted luminaires are suspended
from the ceiling and may light down onto a table, uplight the ceiling, or provide a glow in
all directions. Mount pendants at an appropriate height that will not result in a direct
view of the source and provide adequate lighting levels. For example, in offices, linear
fluorescent luminaires require sufficient ceiling height of 2.6 m (8 ft-6 in) or higher,
although some newer T5 pendants are designed for 2.4 m (8.0 ft) ceilings.
"Energy Management", Lighting Handbook Reference and Application, Chapter 26, Ninth Edition (New
York: The Illuminating Engineering Society of North America, 2000), p. 26-1.