[Radiance-general] Glare and evaluation of lightshelves

[Carlos Ochoa]

Hi there!

I'm using DR 2.0 and I've been making parametric
calculations comparing daylight systems -a room with high
reflectances, and the same room but adding in one case a
lightshelf and in another an anidolic reflector. The room
faces south, and I am evaluating them through daylight
glare index (dgi).

To give more details, the room measures 8x12 meters, with a
ceiling height of 2.70 meters. The window is 8x1.70m
(placed on the 8m side).

The materials: ceiling: brushed aluminium (r=80%), walls:
beige (r=65%) and floor: blue (r=20%). These reflectances
were taken from recommendations from literature. 

The light shelf has a length of 1m and is also made from
brushed aluminium and is placed 2.1 meters from the floor.
(half is inside the room and half outside).

I generated pictures with winrview, both looking into the
window and looking sideways, and then used the two main
glare routines available (findglare and glarendx). 

According to other studies (including those of people who
have used Radiance) the lightshelf should have a lower
glare index than the room without any addition, but to my
surprise and in the two picture cases, it is the opposite!
(absolute illuminance levels are OK, though)

In the beggining I thought that my ceiling was too specular
(50%) but then I changed it to another with similar
reflectance but no specularity... and the results are still
the same!

What could be wrong?

Carlos


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