[Radiance-general] Trans material - single pane of polycarbonate

[Greg Ward]

Hi Erika,

I believe that the "trans" material is a reasonable start for this panel as far as you have described it.

Your material will come out a little low on transmission, since the transmitted fraction of 0.706 multiplied by the color (0.9 or so) comes out to 64% transmission rather than your target of 71%.  This does not explain why your values are so low, but it may have to do with your sampling parameters.  Diffuse scattering from your trans surface implies that an additional "ambient bounce" is needed to account for this light.  Did you try increasing your -ab parameter?

Best,
-Greg

> From: "Erika Saretta" <erika.saretta at supsi.ch>
> Date: March 25, 2017 1:43:06 AM PDT
> 
> HI!
>  
> I am trying to model a panel of polycarbonate (modeled as a surface facing the sun).
> My goal is to determine the annual solar radiation behind it.
>  
> Since I have the following values:
> -          Transmission 71%
> -          Haze 66%
> I am trying to model the polycarbonate as a “trans” material in Radiance.
>  
> Then, I perform the radiation analysis (I use DIVA4RHINO and Daysim model) with the following parameters for the trans material:
>  
> void trans polycarbonate
> 0
> 0
> 7 0.972 0.902 0.835 0.07 0 0.706 0.344
>  
> But… I obtain very low radiation values (from 30% to 50% of radiation loss).
> Does this loss seem unreal as a result?
> Do you think that “trans” material is the right choice for the polycarbonate?
>  
> Any suggestion?
>  
> Thank you in advance
>  
> Erika
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