I am confused about the solar heat gain simulation. As the graph shows, I created two kinds of window construction that had the same panels but different order. So they had the same t-solar and different sghc(since the t-solar is only about the primary solar heat gain).
When I calculated the zone solar heat gain with those two windows, the result is the same. Is that means solar heat gain only consider about the primary solar radiation?
So is there a custom output can be used to calculate the total solar gain through window?
I think I understand why you are confused. Solar Heat Gain Coefficient not only accounts for the solar heat that gets directly transmitted through the window (aka. Solar Transmittance). It also includes the portion of heat that gets absorbed by the window panes and then conducts to the interior under “standard summertime” conditions.
So changing the order of the glass panes won’t really affect the Tsol much or the directly-transmitted solar gain but, if one pane is more absorptive or reflective than the other (which they usually are), this can have a dramatic impact on the absorption and subsequent conduction of heat to the interior.
This is why we have conventions in practice like always putting the Low-E coating on the exterior glass pane.
Thank you @chris, that makes sense.
But I also want to know about the calculation method of “zone solar heat gain” by Openstudio. Does it only contain the directly transmitted solar?
If I want to know the total zone solar heat gain by radiation through the window (which contains the secondary heat gain), which output should I use?
For now, I can only use the “cooling load” to compare those two window constructions, but I think there must be a specific way for solar radiation.
