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

[Christopher Rush]

Erika,
Have you seen a sample of the material? I see you note a Haze value of 66%, which is somewhat telling but not directly transferrable into a radiance definition. Is the material almost completely translucent with almost no specular transmission, or is it partially clear that you can see objects through it? Your trans parameter #7 (you have 0.344) I think implies that the material is transmitting roughly one-third of its transmission as direct and non-diffused transmission (direct view through the material).

I don't think that comment would solve your transmission loss problem, but would be worth a test rendering to see if the light transmission directionality "looks" the way you'd expect.

-Chris

From: Erika Saretta [mailto:erika.saretta at supsi.ch]
Sent: Saturday, March 25, 2017 4:43 AM
To: radiance-general at radiance-online.org
Subject: [Radiance-general] Trans material - single pane of polycarbonate

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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