Hello All,

I am trying to compare the difference in glare given off a building
after a cladding retrofit (from the perspective of occupants in
neighboring buildings). The original curtain wall cladding is a
white/grey marble and glass spandrel panels with a white patterned frit
are proposed for the retrofit. I am using Radiance in IES' Virtual
Environment program; this is my first time using the simulation
software.

I have some questions about determining/selecting material properties,
specifically deciding what material type (plastic/metal) and secularity
to use for the two cladding options.

Specifically how do I choose a realistic secularity value for the
material I am using? Is there a definitive way to select a value or is
it dependant on multiple iterations comparing how the images produced
look? I'm trying to use the program to show me how much glare I could
expect to see, if the results are based on constantly tweaking the
parameters so the image "looks" right for me I don't see how the results
can be accurate.

Is a more extensive database of materials and their properties (beyond
what is provided with the program) available? For the materials
described below what specularity values would you recommend - and what
is the basis behind choosing those values?

My assumptions:

Marble - Originally white, but panels have become grey with dirt over
time, not polished, dull finish

Type: Plastic

Colour: (0.91, 0.91, 0.83)

Specularity: ?????? (I think this may be low because it is not
polished marble)

Roughness: 0.05 (???)

Glass Frit - Composed of: Clear glass, 60% coverage white frit, clear
glass, 100% coverage white frit. From Window 6, I estimate the solar
reflectance of the system to be around 25-35%.

Typle: Metal ??? (Does the frit have specular and diffuse
reflection of light?)

Colour: (1.0,1.0, 1.0)

Specularity: ????? (Clean polished glass)

Roughness: 0.00

If anyone has information from doing a similar simulation or has any
suggestion on what specularity values I should use to model these
materials it would be very much appreciated.

Thanks,

Nastassja