[Radiance-general] Perforated window shading

[Marcus]

Thanks for your response Lars,

Yes, in this case I can comfortably assume that the transmission is uniform
over the surface and will use the trans modifier. My question is, what
transmissivity should I use? If I assume that the void space is 15% of the
area, how shall I define the trans modifier? Is it actually reasonable then
to simply assume transmissivity=85%? We have done this, and the lux values
are lower than expected. What about the transmittedSpecular value?

Are there i.e. any empirical correlations for equivalent transmissivity as
a function of hole size and/or void area ratio?

Thanks again for the feedback!

Marcus
-- 
Marcus Jones,  M.Sc., LEED®AP BD+C
*Freelance energy consultant*
*Vienna, Austria*


On Wed, Feb 22, 2012 at 11:55 AM, Lars O. Grobe <grobe at gmx.net> wrote:

> Hi Marcus!
>
> > I'm doing a daylighting analysis of different facade configurations, and
> > the architect is looking at perforated blinds shading, similar to i.e.
> > this google image I found;
> >
> > http://i01.i.aliimg.com/photo/v0/299829755/perforated_aluminum_blind.jpg
> >
> > Is there any guidance or method to model this concept? Any references
> > you could point me too?
>
> 1) If you can ignore the fact that the perforation leads to a
> transmission not uniformly spread over the blind's surface, but
> concentrated on the holes, you could use a trans modifier.
>
> 2) If you want to consider the pattern created by the perforation (if
> you would look at it from very close distance), you can use mixfunc to
> vary between the reflective surface (metal) and the transmissive holes
> (void). You would need a procedural description of the perforation.
>
> Cheers, Lars.
>
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