[bldg-sim] Lighting Energy

[Smita Chandra]

At 04:03 PM 2/18/2005 Friday, Varkie Thomas wrote:
>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?

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.


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

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.

>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?

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.

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.
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.

>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?

For the occupied periods only, the lighting schedule can be reduced by a 
fraction.  It is as exceptional method under code.

>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.

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.
LEED does give credit for 'daylight glazing' from high windows.. the 
calculation is clearly shown in the LEED manual.

Sincerely,
Smita

>Varkie Thomas
>




======================================================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20050218/18b1858d/attachment-0002.htm>