Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
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.
