[Equest-users] Lighting loads

[Lars Fetzek]

Hello, eQuesters,
 
    I have a few questions regarding how to model lighting loads.  Bear in
mind that I have treated each HVAC zone as a "space" and have modeled
internal walls only along the edges of each such "space" regardless of
architectural reality, so rigorous photometric consideration of daylighting,
etc., would blow my budget with re-work.  Thus, I'm trying to simplify.
 
    First question:
    What exactly is the "Coefficient of Utilization" used in defining a
lighting system?  Is this simply a coefficient used to determine what
fraction of the relevant lighting schedule's "on" time is to be used for
calculating lighting energy use?  For example, if a certain lighting system
is modeled with a certain lighting schedule such that it would consume 100
kWh during a week, but a Coefficient of Utilization for that lighting system
of, say 70%, is used, then does the model then calculate that that lighting
system consumes 70 kWh during that week?
 
    Second question:
    If my speculation in my first question (above) about the effect of the
"Coefficient of Utilization" is incorrect, then what can I do to acheive
that effect?
 
    Third question:
    To acheive the effect discussed in the previous two questions (above) in
particular application to daylight harvesting for LEED(v2.2), I will need to
know what typical values are acceptable to the USGBC.  ASHRAE 90.1 table
G3.1 #6(g) references table G3.2, which does not mention daylighting.  Table
G3.1 #6(f) says that I may model this one of the following two ways:
(1)..."modeled directly in the building simulation"... OR (2)..."modeled in
the building simulation through schedule adjustments determined by a
separate daylighting analysis approved by the rating authority."  At this
stage, option 1 is not realistic.  If I try option 2, can anyone tell me how
to know what "schedule adjustments" are acceptable to the "rating authority"
(USGBC)?  It would be great to have a simple number similar to those in
table G3.2.  By the way, my daylight harvesting occurs in the perimeter of
the building.  If the answer is on the USGBC website, I am clueless on how
to obtain it.
 
    Thank you much for your advice/answers.
 
Lars Fetzek, EI
Phoenix Engineering Group
Tampa, Florida
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