tanks for the advice... i'll try CIE UGR...
.. BUT it seems to me (=super lighting beginner ) that such index is intended
for artificial lighting evaluation ONLY...
i think cie is working to adapt UGR to daylighting purposes..
let me know if you have further informations about
tanks again!!!!
pillo
Pillo,
you are right that the UGR is designed only for artificial lighting glare considerations. theoretically speaking, it can't be applied to assessment of discomfort glare from windows. there are two reasons. firstly, the UGR assumes the light source is very small (<0.01 sr) in the field of view. because windows occupy a larger portion of the field of view, they have a greater impact on the eye's adaptation level, disturbing the assumptions of the UGR. secondly, there is generally greater tolerance for mild degrees of glare from windows than from artificial luminaires. this means that the UGR will overestimate the degree of perceived glare from windows.
given credit where it is due, most of this info came out of the thesis of Martine Velds from Delft, 'Assessment of lighting quality in office rooms with daylighting systems'. the bad news is that she goes on to say that, 'it seems to be infeasible to predict or measure the perceived degree of discomfort glare in a specific situation'. she then went on to develop a new procedure called the 'visual comfort evaluation method', based on scale model or test room evaluations of glare.
so, this is not good news. i'm afraid i don't have a better suggestion as i haven't spent much time on the problem myself. there is, however, a good example of an approach taken by John Mardaljevic in the SIGGRAPH '98 course notes, available on the RADIANCE web-site.
Regards,
Phil Greenup.
At 04:11 pm 18/07/02 +0200, you wrote:
tanks for the advice... i'll try CIE UGR...
.. BUT it seems to me (=super lighting beginner ) that such index is intended
for artificial lighting evaluation ONLY...
i think cie is working to adapt UGR to daylighting purposes..let me know if you have further informations about
tanks again!!!!
pillo
I believe the BRS (British Research Station) glare index is designed
for large areas, like windows. The time I tried to use the BRS glare
calc, though, my then boss, GZ Brown, felt that my prediction of the
index, derived from a Radiance simulation, was too high. I did not,
unfortunately, have time to really research the matter when that
turned up; we went with Brown's preferred method of calculating the
index.
Randolph
Ref: *Daylighting* R. G. Hopkinson, P. Petherbridge, J. Longmore.
London, Heinemann, 1966. (I think that has it--if not, I'd have to
get you a cite for the paper.)