Hi Jia,
EnergyPlus calculates glare index by dividing the window into Nx by Ny rectangular elements and integrating the results. Look at the Daylight Discomfort Glare section of the Engineering Manual for description of the calculation procedures. By splitting a large window into small pieces, I expect to see different glare index calculated. To further identify the potential issues, you can make a few more parametric runs by splitting the large window into 2, 5, and 10 small ones, then look at the glare results to see any pattern.
Tianzhen
On 10/28/2009 12:03 PM, Hu,Jia wrote:
Dear all,
I have a question about Glare Index..
First, I simulate an office with a single big window. The width and the height of the window are 1.8m*1.8, There are interior blinds for this window, the angle is 45 deg. Through simulation, I got a glare index in every hour.
Then, I divided the big window into 3 small windows (each is 1.8 (width)*0.6(height) ) by defining three objects (all of them are windows) in FenestrationSurface:Details. And each small window has the same binds angle and width as the above one.
The problem is that when I ran the two simulations, I found the some differences of glare index in these simulations (only the number of window is different, the total area of the window and all each condition are the same) is nearly 10%. I am confused with this phenomenon.
I also uploaded the two input files and the EXCEL showing the differences to yahoo group at File : /_Problem_Submittals/glare index comparison.zip. You can also download it at URL:
Could anyone explain the reason why the glare index is difference even if the two input files are the same except the number of windows?
Thank you.Jia
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