[Radiance-general] RE: Radiance-general digest, Vol 1 #125 - 1 msg

Tue, 11 Jun 2002 08:13:28 -0400

Thank you Aris.

This is how I had planned to use the info from Optics, that is as a
brtdfunc with glazing.cal.  However glazing.cal is based on fits for
clear and bronze tinted glass only, is it reasonably accurate for more
complex glazing, such as low-e coating?  

Thanks again,

Robert

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Sent: Tuesday, June 11, 2002 6:10 AM
To: [email protected]
Subject: Radiance-general digest, Vol 1 #125 - 1 msg

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Today's Topics:

   1. Radiance and Optics (Aris Tsangrassoulis)

--__--__--

Message: 1
From: "Aris Tsangrassoulis" <[email protected]>
To: <[email protected]>
Date: Mon, 10 Jun 2002 16:26:58 +0300
Subject: [Radiance-general] Radiance and Optics
Reply-To: [email protected]

Dear Robert,

I 'm using frequently Optics software to get data for radiance window
modelling. You can also use WINDOW 4.1 instead. I think that the
BRTDfunc
description of the glazing gives values for transmittance (and
reflectance)
instead of transmissivity (glass material). Naturally there are two
descriptions for front and back surfaces of the window since properties
are
quite different. The description in your example deals only with direct
normal transmittance hence it does not take into account the
transmittance
angular behavior of the glazing. This can be treated as follows: by
using
for example  Window 4.1 you can calculate the transmittance in various
incidence angles. By using a polynomiac interpolation you can create a
function of transmittance versus angle of incidence (i.e. Rdot). In fact
this fucntion is a normalized function because each value is diveded by
the
normal  transmittance. Thus is your BRTDfunc description you should add
glazing.cal function with modified transmittance and reflectance
accordingly.
I hope that this might help.

Aris Tsangrassoulis

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