[Radiance-general] modeling glazings

[Reinhart, Christoph]

Dear colleagues,
 
I know, I know. The topic of modeling glazings in Radiance using Optics 5
data has been extensively discussed in January 2004. I just reread the
emails with great interest in the archives. BUT I am still undecided whether
to go with Optics 5 is worth the effort. 
 
in January, everybody agreed that creating a specific glazing in Optics 5
creates an output as follows:
 
#
# header info
void  glass       TestSystem_glass
0
0
3     0.638     0.647     0.568
 
void  BRTDfunc    TestSystem_front
10
      0.230     0.263     0.326
      0.585     0.594     0.521
      0 0 0
      .
0
9 0 0 0 0 0 0 0 0 0
 
void  BRTDfunc    TestSystem_back
10
      0.289     0.336     0.371
      0.585     0.594     0.521
      0 0 0
      .
0
9 0 0 0 0 0 0 0 0 0
 
Philip mentioned that to use this material description, one would need "two
glass polygons for each window, one for the front and one for the back". I
assume this means:
 
TestSystem_front polygon FrontOfWindow
0 0
12     0     0     0
         1     0     0
        1     1    0
        0    1    0 
 
TestSystem_back polygon BackOfWindow
0 0
12     0     0     -0.01
        0    1    -0.01
        1     1    -0.01
        1     0     -0.01 
         
Is this correct? How does the glazing know its transmittance, i.e. how does
TestSystem_glass come into play? Also, does anybody have any references or
experience how much more accurate a simulation gets if one uses the full
optics 5 file instead of a stripped down version such as:

void  glass       TestSystem_glass
0
0
3     0.638     0.647     0.568
 
Any thoughts are elcome,
 
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)   www.buildwiz.com
<http://www.buildwiz.com/lightswitch/index.cfm>  
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/>  

 
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