Adding spectral data to windows

[Christopher Jones]

Is it possible to add spectral properties to windows using SPOTPro?

The Radiance egroup provided this answer to my query:

As far as I know, you can't export to Radiance from Window, but

you can from Optics. You end up with a simple "glass" definition, and a

front and back material def using the BRTDfunc.

My question to that egroup was:

Is it possible to import or define the spectral characteristics of glazing systems in Radiance? For example, if I define a glazing system with Window 7, is

there a way to enter those properties in Radiance for daylighting analysis?

With SPOTPro can you use the BRTDfunc definitions for windows?

[Zack Rogers]

Hi Chris,

You can use the SPOT Pro material database page to define your own glass in several different ways.

1) The simple glass definition allows you to define a glass material with an RGB transmissivity.  Differing RGB values can be given to model different spectral characteristics - ie. blue or green tints.  This is the same glass definition that would come out of Window 7.  It uses the glass primitive in Radiance that assumes either double pane or single pane, depending on overall transmittance, when dealing with high angle reflections.  These are actually pretty good models of reflection for glass and for me serve most my purposes over the more detailed definition you can get out of Windows 7 which include a front and back reflectance (BRTDfunc) definitions.

2) You can import any BSDF file into SPOT Pro and use as the window material.  These can be imported from the Windows 7 program using the process Reinier described on the Radiance list or from other BSDF sources.  The BSDF must be in the XML format used by Windows 7 and Radiance.  Using a BSDF for a transparent material like glass, though, is typically not recommended as the BSDF definition does not have high enough resolution to capture direct transmittance.

3) If you really need to use the full front and back reflectance BRTDfunc definitions from Windows 7, you could go behind the scenes and add the definition to the Radiance files and then just make sure not to edit from the material editor in SPOT Pro as it won't understand this material type.

Hope this helps!

Zack

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Zack Rogers, P.E., LEED AP BD+C    

Daylighting Innovations, LLC

808 S. Public Road, Suite 200

Lafayette, CO 80026
(303)946-2310

www.daylightinginnovations.com