[BLDG-SIM] Day-Lighting and DOE2.1E

[Reinhart, Christoph]

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
<http://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 at nrc-cnrc.gc.ca 
National Research Council Canada        1200 Montreal Road M-24, Ottawa 
Ontario K1A 0R6 Canada 

Daylighting Analysis Software: 
The Lightswitch Wizard (initial design)
<http://www.buildwiz.com/lightswitch/index.cfm> www.buildwiz.com 
DAYSIM (expert software)                       www.daysim.com
<outbind://26/www.daysim.com>   <outbind://26/www.daysim.com> 


IEA Task 31
http://www.iea-shc.org/task31/ <http://www.iea-shc.org/task31/>  

 
 
-----Original Message-----
From: Varkie Thomas [mailto:Varkie.Thomas at som.com]
Sent: Wednesday, January 21, 2004 4:37 PM
To: BLDG-SIM at GARD.COM
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)



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