[Bldg-sim] interstitial blinds shading

[Lars O. Grobe]

Hi!
> Does anybody model these regularly?
Not regularly, but I have done that for some daylighting simulation. In 
that case, the blinds for rather diffuse and the modeling was not too 
complicated.
> What are the merits of simple vs more computationally expensive 
> modelling methods (e.g. Bidirectional Scattering Distribution Function)?
I am familiar mostly with daylighting applications. You have basically 
three options there. First - geometric model. Leads to lots of geometry, 
and expensive computation and wrong even wrong results under certain 
circumstances (e.g. specular curved blinds and backwards tracing). 
Second - BSDF computed from geometric model. Low-res BSDF (as in Window) 
allow very (!!!) efficient calculations, including annual performance 
assessments, and replace the whole geometry by a material specification 
at the cost of low angular resolutions (e.g. not for glare studies). 
High-res BSDF does not allow the same efficiency for annual simulations, 
but keeps angular resolution. Third - BSDF measured. This ones gets 
clostest to the truth, including all the forgotten effects such as 
manufacturing tolerances, glare and shading caused by detail you would 
not model - and you do not have to believe in the specs, you measure them.
> Are there any well recognized (i.e. mature/ main stream) standards 
> covering blind/ shade glazing combinations?
I would be interested if there are systematic works on this, too!

We are doing BSDF measurements at very high angular resolutions for 
visible light and near infrared at our lab. We are doing so to 
characterize the transmission through the whole unit. However, the 
measurement is covering only radiative transfer, and will not give you 
information about anything inside the unit, which is treated as a black 
box in that case.

Cheers, Lars.