RE: [EnergyPlus_Support] Window Heat Gain of South oriented window

["Christensen, Craig" <craig_christensen@xxxxxxxx>]

If I understand correctly what you describe in your email then ... yes,
these results are normal and explainable.  

 

In the summer (for a northern latitude), the sun passes high overhead
and solar radiation strikes a south-facing window at a very oblique
angle.  Therefore, the intensity of the incident radiation is
significantly reduced (the direct beam radiation is multiplied by the
cosine of the incidence angle).  Window heat gains also depend on the
sky diffuse and ground-reflected radiation and the reflection,
absorption, and transmission of the radiation as it passes through the
window glass, but the effect of sun angle on the incident radiation is
the dominant effect in the month-to-month variation (see the figure).
The fact that south-facing windows have higher gains in winter and lower
gains in summer is a key principle for passive solar heating of
buildings.  Shading devices above south windows (overhangs) also take
advantage of high sun angles to provide summer shading and further
reduction of window heat gains.

 

Craig

 

 

 

 

 

________________________________

From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of anarui.oliveira
Sent: Wednesday, December 26, 2007 11:31 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Window Heat Gain of South oriented window

 

Greetings!
I'm just starting now with E+ and I tried out some basic configurations 
(basicaly a box with a window) in "free" simulation mode (no heating or 
cooling) which returned some awkward results:
- A south oriented window, with no shading of any type, returned lower 
Window Heat Gains in a Summer Week than in a Winter Week (I checked the 
Direct and Difuse Solar and they are lower in Winter, as would be 
expected);
- And also the same window returns larger Window Heat Gains as I a 
rotate the exact same building (rotation relative to the North) as to 
rotate the window to East or West (as I rotate the building, the 
strange Summer-Winter behaviour also diminishes and eventually 
vanishes);
Are these results in any way normal or explainable? Any idea what I 
might be doing wrong?
I appreciate all help I can get. Thanks!

 



[Non-text portions of this message have been removed]



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