Autodesk 256B1-05A761-1301 - AutoCAD Revit Structure Suite 2010, User Manual

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Light Loss Factor Parameters
When you turn on a lighting fixture, light travels through the light source (lamp or ballast) and the lighting
fixture (such as a lamp shade or lensed troffer), until it reaches the work plane where it is needed. Along the
way, the amount of transmitted light is reduced, obscured by the light source, the lighting fixture, and other
environmental factors. The Light Loss Factor measures the reduction of light as it travels from the light
source.
When defining the Light Loss Factor for a light, define the parameters as follows. Check with the lamp
manufacturer for the appropriate Light Loss Factor values for a particular type of lamp.
Description Parameter
For fluorescent light sources, a measure of the amount of light lost or gained
due to deviations above or below the ideal operating temperature. Valid Temperature Loss/Gain Factor
values are between 0 and 2. A value of 1.0 indicates that no light is lost or
gained due to temperature changes. Values greater than 1.0 indicate an
increase in light. Values less than 1.0 indicate a loss of light.
A measure of the amount of light lost or gained due to fluctuations in voltage
delivered to the light source. Valid values are between 0 and 2. A value of Voltage Loss/Gain Factor
1.0 indicates that no light is lost or gained due to voltage changes. Values
greater than 1.0 indicate an increase in light. Values less than 1.0 indicate
a loss of light.
Lamps and ballasts experience losses when operating together as a system.
The Ballast Loss Factor is the percentage of a lamp’s initial rated lumens Ballast Loss Factor
that is produced by a given ballast. Valid values are between 0 and 1. For
example, a value of 0.95 indicates that the ballast produces 95% of its initial
lumens and loses 5%.
For metal halide lamps, a measure of the amount of light lost due to the
position of the lamp. A decrease in light occurs when the angle of the lamp
shifts the cold spot of the bulb. Values less than 1.0 indicate a loss of light. Lamp Tilt Loss Factor
A measure of the amount of light lost due to deterioration of the surfaces
of the lighting fixture as it ages. For example, blemishes and discolored Surface Depreciation Factor
shielding materials change the amount of light emitted. Values less than
1.0 indicate a loss of light.
As a lamp ages, it produces decreasing amounts of light on a predictable
curve. A typical strategy is to use an average Lamp Lumen Depreciation Lamp Lumen Depreciation
(LLD) value at 40% of its life. Valid values are between 0 and 1. For example,
a compact fluorescent has an LLD factor of 0.85, indicating an average
output at 85% of its initial lumens, losing an average of 15% over its life as
the lamp ages.
A measure of the amount of light lost due to environmental dirt and dust
that is trapped by the lighting fixture. Valid values are between 0 and 1. Luminaire Dirt Depreciation
For example, a value of 0.9 indicates that the fixture produces 90% of its
initial lumens and loses 10% due to trapped dust and dirt.
A measure of the amount of light produced by a lamp, taking into account
various environmental factors that obscure or reduce the emitted light. Total Light Loss Factor
When the Method is Simple, use the slider or text box to specify a value.
When the Method is Advanced, this parameter displays a read-only value,
Creating and Modifying Lighting Fixtures | 1187