Question about Radiance Glass Modifer Properties

Hi @chris and @mostapha
I am running an annual daylight study for a Honeybee model of a room in my project. In the Technical document for window specifications of project, I have Glazing Transmission and Internal reflection which I want to set in Grashopper. But in the “HB Glass Modifier” componant there is no input for reflection.
Could you please tell me how Glass Reflection is considered in this componant and if there is any way that I can set it?

window specifications

I also have another issue about face attributes. When I have a single HB room, all the faces (wall, aperture,roof,floor) are considered as “Outdoor” Boundry Condition. So I should use " HB Exterior Modifier Subset" componant to define faces reflection. But this value that I set, is for interior face of wall or exterior face or both?
Because for me the interior face is important but I dont know how to set it.

Thanks for your consideration.

Hi @FatemehMohseni ,

The Radiance Glass Modifier has built-in properties for reflection that make sense for clear float glass. If you really need to change the reflectance, then the Radiance Translucent Modifier gives you full control of all transmission and reflection.

Hi @chris
Thanks for your response.
May I ask how much is the reflection of clear float glass? around 4%?
Could you please help me also with the second issue I asked about interior face reflection? The number we set for wall reflection is used for interior face of wall or exterior face or both are the same?

You’ll have to check the Radiance documentation or search the Radiance forum. I see Greg, the author of Radiance, answers a lot of questions about it here:

And please try to keep the discussion to one topic per discourse topic. Open another topic if you have a different type of question.

Hi @chris
Thank you very much for your consideration.

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Hi @chris
I checked “HB Translucent Modifier” and I have a doubt about it. Could you please tell me why reflectance and transmittance inputs are diffuse-ref and diffuse-trans. But in the " HB Glass Modifier" the input is trans? What is the difference between transmittance and diffuse transmittance here?

Hi @FatemehMohseni ,

I’m not sure what I could say to make it clearer. Maybe it helps to know that some people refer to the “specular” portion as “Beam” transmittance. Just doing a google search of the terms “specular and diffuse” would probably help. Or searching these terms on the Radiance forum.

Great. Thanks for your help.