[bldg-sim] Lighting Energy

Varkie Thomas Varkie.Thomas at som.com
Fri Feb 18 13:03:11 PST 2005


Who should I contact at IECC for interpretation of the code?  In the
meantime I have some questions (pardon my ignorance) regarding lighting.

 

IECC-2000, page 114, table 805.4.2 (also in the Chicago Building Code)
shows the following lighting power densities for office building:

 

Entire Building:                                      1.3 W/ft2

Tenant Area or Portion of Building:       1.5 W/ft2

 

There is a Note "b" associated with office (and also classrooms/lecture
halls) which states: 

 

"Where lighting equipment is specified to be installed to meet
requirements of visual display terminals as the primary viewing task,
the smaller of the actual wattage of the lighting equipment or 0.35
W/ft2 times area of space that the lighting equipment is in shall be
added to the interior lighting power determined in accordance with this
item"

 

I assume that the entire building area is the gross area which includes
the core (elevator & duct shaft plan sections) and underground parking.
The net area is about 15% less than the gross area and this would be the
tenant area.  1.3 W/ft2 * 1.15 = 1.5 W/ft2

 

Is the "lighting equipment" task lighting only, or does it include other
equipment such as projectors?

Are computer monitors (visual display terminals) a "lighting equipment"
since it also generates light?

 

What is "the smaller of the actual wattage of the lighting equipment or
0.35 W/ft2 times area of space that the lighting equipment is in shall
be added to the interior lighting power"?  Given a tenant space of 100
ft2 that has 1.0 W/ft2 general lighting and a 100 watt task light, what
is the area lighting of the space for code compliance?

 

Is there a lighting program or Excel spreadsheet program that will
calculate the W/ft2 at the ceiling given the illuminance required at the
task level, the type of lighting fixture or luminaire, and the ceiling
height?  I think manufacturers should provide this calculator for their
luminaires.

 

How would you show energy savings for occupancy based lighting controls?
In 10CFR435 Table 514.1 "Power Adjustment Factor (PAF)", the PAF for
Occupancy Sensor is 0.3.  When using energy analysis programs, can we
reduce the lighting schedule fractions by 30% for the proposed design
compared to the prototype or base design?

 

Increasing the percent glass of the envelope and increasing the ceiling
height also reduces lighting usage because of increased daylighting.
Daylight can now reach deeper into the interior.  How would you show
this energy savings using computer programs?  Can the perimeter zone
depth be increased to say 30 feet?  The DOE2.1E program lets you locate
two light sensors in the perimeter zones but the codes do not specify
where in the zone. They could both be located 5 feet from the window as
representing the entire perimeter zone depth.

 

Varkie Thomas

 



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