[Radiance-general] Model a Double glazing window

[Jack de Valpine]

Hi Raghu,

Here are a couple of things to think about.

MODEL GEOMETRY
Based on your description, I am guessing that you are using genbox to 
model each sheet of glass in your insulating glass unit. The radiance 
materials that can be used to describe glass, such as "glass" and 
"brtdfunc" are designed to be applied to a surface as opposed to a 
volume. Using genbox will give you a volume, applying a "glass" material 
with a specific transmittance to that volume will not give you the 
correct resulting transmittance because rays are going through two 
pieces of geometry. In order to get the correct transmittance for a 
given glass material you would need to use a single surface to describe 
the geometry.

GLASS MATERIALS
If all you care about is transmittance through a insulating glass unit 
composed of two layers of glass, there are a variety of ways to to come 
up with a material description. The resulting transmittance of a 
specific makeup should either be available from a manufacturer or can be 
calculated with an application like Windows or Optics (both available 
from LBNL). Note that for the glass material type transmittance needs to 
be transformed to the Radiance term for transmissivity. If you also need 
to more carefully account for reflectance for such a glazing unit, 
assuming you are using Radiance on Linux, then you can use the "glaze" 
script that comes with Radiance. To learn more about how to use the 
script, you can check out my blog post:

    http://modsimvis.blogspot.com/2014/12/glass-in-radiance.html

Best,

-Jack de Valpine,
Visarc Inc


On 12/18/2015 12:34 PM, raghuram kalyanam wrote:
> Hi Every one,
>
> I want to model a Double glazing window which contains glasses with different transmittances. I did the following
>
> 1. window.rad -- included the properties of materials such as window frame, glass1 and glass 2
> 2. glass.rad -- position of glasses using genbox
> 3. frame.rad -- position of frame using genbox
>
> then made octree of altogether.
>
> Please let me know if  this is the  right way or if not please suggest a better one.
>
>
> Best Regards,
> Raghu
>
>
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