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Dear
Varkie,
I
agree with Jon that
(a)
Sensor placement has a huge impact on the results.
(b) I
wouldn't expect that [not providing a geometry] would be an acceptable
method since you really do not know what you are
modeling.
With
respect to your earlier question I believe that even if you do provide geometry
data, DOE2 saving predictions will be on the optimistic side. One flaw of
basically all simulation programs that predict electric lighting savings due to
lighting controls is that they tend to compare an ideally dimmed lighting system
with a lighting system as is permanently switched on during occupied hours. This
leads to overly optimistic savings, as the IESNA handbook rightfully states: "an
undimmed lighting system with a regular on/off wall switch should be the
reference system". To be able to compare results to manually controlled
lighting, you need a user behavior model that predicts how individuals interact
with their manual lighting controls. Another aspect you should pay attention to is the blind
control algorithm. If the blinds are permanently retracted, you will again
predict wildly overoptimistic savings. I think there is a way in DOE2 to set the
blind control to manual.
If you
want to develop a feeling for electric lighting savings due to controls, you
might want to use the Lightswitch Wizard, www.buildwiz.com, a simple online
daylighting analysis tool that is based on pre-calculated RADIANCE simulations
and a manual lighting control model. The model has been developed based on field
data from several countries and is currently further refined within
International Energy Agency's Task 31, Daylight Buildings in the 21st
Century.
Christoph
Christoph Reinhart,
Ph.D.
tel: (613) 993-9703
Research Officer fax: (613) 954-3733 Institute for Research in Construction e-mail: christoph.reinhart@xxxxxxxxxxxxxx National Research Council Canada 1200 Montreal Road M-24, Ottawa Ontario K1A 0R6 Canada Daylighting Analysis
Software: IEA Task 31 http://www.iea-shc.org/task31/ -----Original Message-----
From: Varkie Thomas [mailto:Varkie.Thomas@xxxxxxx] Sent: Wednesday, January 21, 2004 4:37 PM To: BLDG-SIM@xxxxxxxx Subject: [BLDG-SIM] Day-Lighting and DOE2.1E Can day-lighting controls be considered for LEED certification under "Energy & Atmosphere - Optimize Energy Performance"? If so where should the light sensor be located in the space? Is there any energy code that allows credit for day-lighting controls? The DOE2 program allows two light sensors per space. Supposing the two sensors are located 5 ft and 10 ft from the window. Is the average daylight at these two points used in determining the reduction in artificial lighting?
The DOE2 program expects zones to have 6 surfaces defined with X,Y,Z coordinates and reflectance values for day-lighting analysis. Ignoring this produces warning messages but the results show a reduction in artificial lighting energy. For day-lighting analysis we only enter into DOE2 the X,Y coordinates of the window origin relative to the wall and also the wall and window dimensions. Can we assume that the energy savings results from the DOE2 program are on the safe side (the actual energy saved is more) when we use the program without all the surfaces and coordinates?
Are there any rules for day-lighting analysis for establishing energy savings and for comparing the results from different studies?
Varkie Thomas Skidmore, Owings & Merrill LLP Tel: (312) 360-4467 (direct) =====================================================You received this e-mail because you are subscribed to the BLDG-SIM@xxxxxxxx mailing list. To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE@xxxxxxxx ====================================================== You received this e-mail because you are subscribed to the BLDG-SIM@xxxxxxxx mailing list. To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE@xxxxxxxx |