[Bldg-sim] Radiance: Determining Specularity Values - Spandrel Panels: Marble vs Fritted Glass

[Pearson, Nastassja]

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

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