Solar Gain Factor & Variable Infil Values

3 posts / 0 new
Last post

am a eQuest newbie, am doing some research wherein i need to know the solar
gain factor the windows use, also does eQuest take into account Alternating
Solar Gain Factor???I would also like to find out whether variable
infiltration flow rates (or variable ventilation values) are taken into
account??? the hourly report block i generated only gave me same value for
infiltration flow rates for all 24 hrs & for all 365 days.

Please help, this is regarding my Major Project at College & deadlines are

Thanks in advance,

Piyush Varma

Piyush Varma's picture
Joined: 2011-09-30
Reputation: 0

Piyush, I am but a humble user and not a developer or "expert," but I
can offer some fast suggestions - someone else may care to elaborate:

1. The solar heat gain factor (SHGF) used depends on the window
selected. Suggest checking out the DOE2 Glass Library if you haven't
already. Right-click nearly any input field, select "Tutorials and
Reference" from the context menu, and select the DOE2 Glass Library
excel spreadsheet.

2. If you asking whether the variability of solar heat gain (that
is, transmitted + absorbed radiation that flows inward) through a window
is accounted for, then the answer is yes. That varies hourly based on
the changes of incident sunlight, as affected by the fixed window
orientation, any building shades and/or other self-shading elements. If
instead you mean a variable shading coefficient (SC), as with automated
blinds and such, then the answer is also yes - via creating a custom
shading schedule.

3. Variable infiltration and ventilation rates are both model-able
in eQuest, and are two distinct topics...

a. For infiltration, suggest entering the detailed mode, opening
the properties for any space under "internal loads" tab, and exploring
the various infiltration methods that may be employed under the
infiltration tab, along with the corresponding help/dictionary entries.
The ACH rate method for example accounts for the hourly wind speed data
present in your weather file to determine the hourly ventilation rate.

b. For ventilation, you may observe "constant" ventilation rates,
but only if you chose to model as such. Be sure any and all methods of
varying the ventilation air rate are accounted for in your model.

Best of luck!


Nick-Caton's picture
Joined: 2011-09-30
Reputation: 605

Hi Piyush,

Apologies, I wasn't sure whether you meant SHGF.

I did some googling to check my vocabulary and found this reference: Comp Analysis Table.pdf

It looks like: Solar Gain Factor (S Factor) = Shading Coefficient (SC)
* 0.87

I can add that: Shading Coefficient (SC) = (Center of Glass SHGF) /

So to answer your first question, while this is the first time I've
personally run into S Factors, it would appear they're analogous to a
center-of-glass SHGF, but can vary based on external shading devices
(including trees, curtains and shades) per the above. I'm copying
eQuest-users to share the following procedure and to allow others to
correct any misunderstandings we may have regarding what S Factor really
means - I hope you don't mind!

So per your second inquiry to determine the hourly S Factors, and
because I was curious, here's a procedure:

- Set up your windows and all variable shading items.

- Create an hourly report/block for the window(s) in question
selecting the items shown in the screengrab below - SC and "Value by
which..." SC multiplier for those of you in the archives.

- Run the simulation and open the hourly results up in excel
(hit the 'hourly results' button in the sim viewer).

- Multiply those values across to get your hourly effective SC,
and again by 0.87 to get an hourly S Factor.

Best of luck,


Nick-Caton's picture
Joined: 2011-09-30
Reputation: 605