The window “properties” may be the same on
input but these are characterized for normal incidence. However in energy
modeling, windows rarely experience the sun shining at right angles to the
window. I suspect the two programs differ in how they model transmission at higher
incidence angles.
From:
Sent: Wednesday, July 21, 2010
8:07 AM
To:
Subject: [EnergyPlus_Support]
Energy Plus vs TRNSYS
Hello,
New to Energy Plus, I learn how to use the software by simulating a basic
building (parallelepiped with windows and internal gains). I use HVAC template
HVACTemplate:Zone:IdealLoadsAirSystem to determine heating and cooling needs.
To confirm my simulation, I have a reference building simulation done under
TRNSYS.
For the weather file, I have used the weather converter tool (provided by E+)
to convert a .tm2 file into a .epw one.
My results show a big difference in the cooling need between the 2 simulators.
After investigation, it appears that the zone solar transmitted energy results
could be the reason for this difference. E+ computes around 15% more solar
transmitted energy than TRNSYS.
As the windows characteristics are identical between both simulators, I am
wondering if the weather files are really identical? How can we be sure that
they are identical?
What should I check if the problem is not related to the weather files?
Many thanks for your help.
Herve
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