Description of complex glass systems (geometry + material)

Hi everybody,

I have two questions about the description of a glass facade with a
complex glass system: one about the geometry and one concerning the

1-. With the objective in daylight calculations and daylight efficiency
of materials I try to simulate, so accurate as possible, a doble glazing
facade with the next composition:

9mm laminated glass with spectrally selective interlayer -- 16mm air --
4mm float glass

All the papers I've read describe the glass geometry as polygon as follows:

mod polygon id
3n x1 y1 z1
    x2 y2 z2
    xn yn zn

In my case, with such a glass system, would be this geometry
description of the glass right and accurate? or should I define the
radiance geometry like the contructed geometry?

2-. The second question is about the material description.
I have measured the transmittance of this doble glazing material sample
with a Spectrometer and an accessory for external measurements and
computed its transmissivity.
The complete definition of the material that I get is as follows:

mod glass id
3 rtn gtn btn

On the other hand I have exported in Radiance format from the software
Optics5 a similar glass, also with sun protection interlayer, and the
material description is much complexer. It is as follows:

void glass sunstop-t-silver-20_glass
3 0,205 0,222 0,239

void BRTDfunc sunstop-t-silver-20_front
      0,325 0,281 0,197
      0,188 0,203 0,219
      0 0 0
9 0 0 0 0 0 0 0 0 0

void BRTDfunc sunstop-t-silver-20_back
      0,259 0,289 0,307
      0,188 0,203 0,219
      0 0 0
9 0 0 0 0 0 0 0 0 0

My question is if the description I did is complete and will give an
accurate calculation.
In case it is not, how can I get the hole description with the BRTD
information if I just have the glass sample and the Spektrometer to
start and this glass is not in the IGDB?

Thank you,



Dipl. -Ing. (-Arch) Marina Aviles Olmos
Institute for Lightweight Structures and Conceptual Design (ILEK)
University of Stuttgart
Germany (Radiance Mailing List)