ANALYSING RADIATION TRANSPORT THROUGH
COMPLEX FENESTRATION SYSTEMS
N.S. Campbell and J.K. Whittle
Thanks for that.
Interestingly the v. helpful C & W paper, although
expressing sentiments that are bang on target,
seems to compare one simulation with another,
but not with real-world empirical data, unless I�m
Maybe up to some point, comparisons of their
Monte Carlo results with some similar simulation
in Radiance could be interesting/useful, but surely
not as useful as comparison with some real-world
Desperate for any kind of confirmation, my very
rough lux-meter measurements of office blind
overall transmission on an overcast London
day compared tolerably with their simulations.
I�m hoping some better real-world data will
come to light eventually.
.... just how useful is a daylight factor
evaluation for the scenario you describe.
Surely, the blinds are there also to control
direct sunlight? Perhaps even it is their
On the subject of control of direct sunlight by
blinds; despite having more than a suspicion
that you know more about daylighting than
I do, here goes:
The reason I said I was �not interested� in
direct sunlight in those studies was that for me
at least, in the UK, the �overcast sky� is the most
useful environment to apply in daylight studies
at the early stages of building design development.
It allows alternative architectural designs to be
compared for degrees of compliance with
particular published UK CIBSE and BCO
criteria so as to merit the alternatives'
I find that the usual objective for these sorts of
study is to find the daylight factor with �venetian
blinds down, slats horizontal, overcast sky�.
The control of direct sunlight by the venetian
blinds need not figure in these early simulations,
despite that being their major function.
Any fixed solar shading does of course have
to be modelled reasonably well, as do the
relevant parameters for the solar transmission
of the fa�ade and glazings; the geometry and
reflectance of the building model and its context.
Agreed nevertheless that if one could develop
a function to simulate blinds, then not allowing
the direct factor to be simulated would be
Regards, George Chadwick
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