Using Radiance to generate solar surface gain schedules

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Looks like you're wanting to use Radiance and EnergyPlus together, perhaps with OpenStudio? If so, the built-in "Radiance Daylighting Measure" creates a simple glazing material (Radiance 'glass' or 'trans' primitive) based on the VLT of the window construction found in the OpenStudio model. While Radiance does look at the full spectrum, you'll find many of the inputs for materials are concerned mainly with the visible.

While it's true that windows are typically modeled as a single polygon with Radiance, for the utmost accuracy you should use two if you're doing an actual IGU. But of course, you need the right inputs, then. What I typically do is get the SHGC, U-value, and VLT for the whole unit (IGU) and plug those into a simple glazing material for EnergyPlus, and a single glass material applied to a single polygon in the Radiance model (and this is how the Radiance measure works). If you do not have those values, i.e., you are modeling some experimental system or doing an optimization on the UGU's components, you will need to use LBL's Window and Optics programs to mock up your components and get these values that way. Or take a wild guess. =)

Unfortunately, there is no way to use a custom glass material in the Radiance measure workflow. If you are trying to use this measure, we can talk further about how you might enable that.

P.S. There is a bit more info on the Radiance glass modeling details in this post.

Hi Kostas, You can generate layer absorption coefficients by incident angle with window. In Window preferences turn on "create debug output" in the options tab. Then in optics tab turn on "use matrix method for specular glazing".

Then run the calc for the IGU in Window.

in the directory: C:\Users\Public\LBNL\WINDOW7.6\BSDFs you'll find {systemname}_0_AngularData.csv That csv file will have absorption coefficients for each layer. Below I've pasted the column names in the angular data file for your reference. The columns with absorption are named g1-[fb]Abs[1-9] where [fb] indicates front or back incident direction (you almost certainly want front) and [1-9] indicates the surface.

You can use those coefficients to calculate total absorption by integrating the energy in all incident angles.

Andy

columns in the Angular Data csv file: n Theta Phi g1-SHGC g1-Tfsol g1-Tbsol g1-Rfsol g1-Rbsol g1-fAbs1 g1-bAbs1 g1-fAbs2 g1-bAbs2 g1-Tfvis g1-Tbvis g1-Rfvis g1-Rbvis g1-Tdw-K g1-Tdw-ISO g1-Tuv