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At 04:03 PM 2/18/2005 Friday, Varkie Thomas wrote:<br>
<blockquote type=cite class=cite cite=""><font face="Times New Roman, Times">Who
should I contact at IECC for interpretation of the code? In the meantime
I have some questions (pardon my ignorance) regarding lighting.<br>
<br>
IECC-2000, page 114, table 805.4.2 (also in the Chicago Building Code)
shows the following lighting power densities for office building:<br>
<br>
Entire</font>
Building:
1.3 W/ft2<br>
<font face="Times New Roman, Times">Tenant Area or Portion of
Building: 1.5 W/ft2<br>
<br>
There is a Note “b” associated with office (and also classrooms/lecture
halls) which states: <br>
<br>
“Where lighting equipment is specified to be installed to meet
requirements of visual display terminals as the primary viewing task,
<b>the smaller of</b> 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”<br>
<br>
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<br>
<br>
Is the “lighting equipment” task lighting only, or does it include other
equipment such as projectors?</font></blockquote><br>
It usually includes task lighting only on the assumption that it would be
used on the task lighting schedule in sync with general lighting.
Projectors are used intermittently and can usually be ignored. Even
if they are used very often and considered, they probably fit better into
the equipment loads.<br><br>
<br>
<blockquote type=cite class=cite cite=""><font face="Times New Roman, Times">Are
computer monitors (visual display terminals) a “lighting equipment” since
it also generates light?<br>
</font></blockquote><br>
The intent of the lighting load is to simulate energy usage and heat gain
from the lights. The computer monitors do not really fit that
category (unless the computer monitor is being treated as a source of
light instead of say an overhead lamp, which does not seem very
likely). Computer monitors again would be more appropriately
accounted for in equipment.<br><br>
<blockquote type=cite class=cite cite=""><font face="Times New Roman, Times">What
is “<b>the smaller of</b> 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?<br>
</font></blockquote><br>
If the task lighting is already designed, then that actual wattage is the
design case lighting. In that case, if the design lighting is
higher than 0.35 W/ft2, the code lighting is 0.35 W/ft2; if the design
lighting is less than 0.35 W/ft2, then the code case lighting is coded
same as the design lighting. In other words, you do not get credit for
reducing task lighting below 0.35 W/ft2, but you do get penalized for
going over.<br><br>
If the task lighting is not designed yet, both design case and code case
can assume 0.35 W/ft2 if it is definite that there will be some, as yet
undetermined, task lighting in that area.<br>
If there is going to be no task lighting in that area, both the design
case and the code case should not have the task lighting load included.
<br><br>
<blockquote type=cite class=cite cite=""><font face="Times New Roman, Times">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.<br>
<br>
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?</font></blockquote><br>
For the occupied periods only, the lighting schedule can be reduced by a
fraction. It is as exceptional method under code.<br><br>
<blockquote type=cite class=cite cite=""><font face="Times New Roman, Times">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.</font></blockquote><br>
ASHRAE Std User's manual defines the perimeter zone as 15 feet
deep. The sensor should be located well inside this zone, that is
10' inside, or at the very least, halfway inside at 7.5' to get a fair
idea of energy savings from daylight for the entire zone.<br>
LEED does give credit for 'daylight glazing' from high windows.. the
calculation is clearly shown in the LEED manual.<br><br>
<font face="Times New Roman, Times">Sincerely,<br>
Smita<br><br>
<blockquote type=cite class=cite cite="">Varkie Thomas<br>
</font></blockquote>
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