[Radiance-general] Re: Glazing transparency/reflectivity study

[Galen Burrell]

Thanks Jack.

All seems clear and I've got some results that I'm pretty happy with.  One thing I'm still a little unclear about is how you would apply a low-e film to a non-clear glass (i.e. tinted green, blue, etc) if the script requires one surface to be "clear" for each pane.

For example:
VE2-2M (http://www.viracon.com/makeupsheet.php?id=3840) has the VE-2M coating applied to Evergreen glass on the #2 surface.  As it is now, I would input:
Surface 1 - Clear
Surface 2 - VE2-2M on evergreen (from optics 5 data)
Surface 3 - Clear
Surface 4 - Clear

Is there an easy hack to make Surface 1 evergreen instead of clear?

Thanks,
Galen


-----Original Message-----
Date: Thu, 15 Jan 2009 21:07:06 -0500
From: Jack de Valpine <jedev at visarc.com>
Subject: [Radiance-general] Re: Radiance-general Digest, Vol 59, Issue
        8
To: Galen Burrell <Galen.Burrell at arup.com.au>
Cc: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <496FEBCA.70906 at visarc.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi Galen,

No problem.

Regarding the header

    * Rc<r,g,b> - these are the rgb components for the reflectance on
      the "coated" side of the monolithic glass
    * Rg<r,g,b> - these are the rgb components for the reflectance on
      the non-coated side of the monolithic glass
    * T<r,g,b> - these are the rgb components for the transmittance for
      the monolithic glass
    * Part - this is a boolean value
          o 0 means this is a regular glass
          o 1 means this is a frit - if this is the case the "coated"
            side reflectance needs to represent the reflectance of the
            frit at 100% coverage which should be possible to extract
            from the glazing manufacturer

The RGB values are extracted from the file generated for a "radiance"
export from Optics. This should be for a single pane monolithic glass
description (not a multi-layer make-up). The file will have three
Radiance material definitions, the two BRDTfunc definitions are the ones
to pay attention to. The makeup is something like the following:

    void BRTDfunc some.glass.front
    10

        Rfr Rfg Rfb
        Tr Tg Tb
        0   0   0
        .

    9 0 0 0 0 0 0 0 0 0

    void BRTDfunc some.glass.back
    10

        Rbr Rbg Rbb
        Tr Tg Tb
        0   0   0
        .

    9 0 0 0 0 0 0 0 0 0

So you need to take the two rgb triples for reflectance and one for
transmittance. So an entry in the data file could look like this (you
will need to figure which represents the coated side if needed):

    Surface Tr      Tg      Tb      Rcr     Rcg     Rcb     Rgr     Rgg     Rgb     Part
    <name>  Tr  Tg      Tb      Rfr     Rfg     Rfb     Rbr     Rbg     Rbb     0



A file for a double pane insulating unit might look like the following:

    Surface Tr      Tg      Tb      Rcr     Rcg     Rcb     Rgr     Rgg     Rgb     Part
    green-lowe  Tr      Tg      Tb      Rfr     Rfg     Rfb     Rbr     Rbg     Rbb     0


The glaze script contains a default "clear" glass. I seem to recall that
this is required for the script to output a material description (eg it
must have a "clear" glass description"). If this is not suitable the
script requires some modification, which I think I can offer some
guidance on so that you can include your own "clear" glass description.

I would suggest before you do anything else you should test out the
script as is with the built in values. This will let you see how it
works. You will assign different materials to different layers to build
up the composite unit.

Try it out and let me know if you have more questions.

-Jack


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