[Radiance-general] Modeling glare from light fixtures

[Chien Si Harriman]

Hi-

 

A question to the radiance community.  I've been tasked with modeling a
T5 light fixture in its housing.  This is new for me as a project in
Radiance, as I've largely used it to model natural daylight only, with
the use of imported .IES files when needed.  I believe that I have to
model the light fixture and its associated housing because, for this
high-end conference room, the client for whom I am working is concerned
about glare emanating from the fixture during video conferencing.  The
.IES files just don't have that type of information, as they are really
(at least in this case) files that really just describe the flux as a
mathematical model, and does not physically model the interactions of
the light bulb in its housing.  As a result, I can't really show glare
emanating from the fixture at all!  (these are all things I'm sure you
are already aware of)

 

I am wondering a couple of things, and am looking for some advice,
reactions, precautionary tales, etc. based on the information that I
currently have at hand.  I'm willing to take harsh criticism so lay it
on me.

 

It seems my most accurate option is to model a T5 fixture as a glow
object, giving off the appropriate luminous flux inside of a reflective
housing.  I would likely have to take some guesses as to the geometry of
the fixture just because, at least at this time, I don't have a physical
sample of the fixture, nor do I have any sort of exploded orthgraphic
projection showing the inner details of the fixture.  I'd likely take
just a section of the fixture (found on the cut sheet) and extrude it
the appropriate length.  My biggest concern is in regard to modeling
such a high intensity of light in such a small confined space with so
many bounces of light.  I am not sure if there are "standards" in terms
of simulation settings, or other helpful pointers, that would normally
be applied to simulate the fixture in this way.

 

The other option, far simpler though possibly just as effective (and
this is a huge possibly in my mind), is to simply place a square
luminous glow object over the fixture where the light would normally
exit the fixture.  I suppose I could build up my own mathematical
representation of how the glow object should distribute its light (in
effect build my own .IES file (of sorts).  Though, I truly have never
done this before and I would assume there is a chance of error.  Any
guidance for how to go about this would be appreciated, perhaps a
reading supplement to the Ward & Shakespeare book to ground my thinking,
at the very least.

 

 

As always, your help is appreciated.  

 

 

 

 

Chien Si Harriman   LEED AP

Senior Building Performance Engineer

(P) 415.655.4005 

GUTTMANN & BLAEVOET Consulting Engineers

San Francisco | Sacramento | Santa Rosa <http://gb-eng.com/page/Contact>
| Walnut Creek <http://gb-eng.com/page/Contact>  | Website
<http://www.gb-eng.com/> 

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HVAC, Plumbing, Fire Protection, Electrical, Lighting,
Telecom/Technology <http://gb-eng.com/page/services> 

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Modeling <http://gb-eng.com/page/services> 

 

 

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