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Material Definition In Radiance

asked 2015-06-25 19:35:42 -0500

Sara_M gravatar image

updated 2015-07-10 09:12:32 -0500

Hi,

Please explain where I can define color of surfaces and their reflectivity properties in OpenStudio which is necessary for radiance simulation?

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answered 2015-06-29 10:19:04 -0500

updated 2015-06-29 10:45:38 -0500

David is correct as far as the lack of color support for Radiance (and EnergyPlus for that matter); OpenStudio's Radiance models are greyscale. There are several reasons for this, primarily the lack of spectral resolution in the visible range in both the EnergyPlus and OpenStudio models.

Unfortunately, David's advice of setting reflectance is incorrect/incomplete. The image link in his reply showed the input fields for a glazing material, which does have reflectance fields, in addition to transmittance fields. However, the reflectance of opaque materials is specified by setting the visible absorptance of the material. This field appears when defining an opaque material, as shown below:

Defining an Opaque Material

The inverse of this value is the visible reflectance, and is used by the OpenStudio-->Radiance translator to define a Radiance plastic material.

When specifying glazings, I would expect your primary interest from a Radiance perspective is the visible transmittance and whether the material is specularly transmitting (clear) or diffusely transmitting (translucent). For these the pertinent entries in the material definition sub-tab are Visible Transmittance at Normal Incidence field and the Solar Diffusing option switch. If "Solar Diffusing:" is set to on, then a Radiance trans material is created; if this is set to off, Radiance glass is used.

Defining a Complex Glazing Material

Be advised, the transmittance of your construction is based on the total of all the material layers. If you do not need to specify diffusely transmitting glazings, I recommend you use the "Simple Glazing System" window material in OpenStudio, which takes just three arguments, the VLT, the U-value and the SHGC:

Simple Glazing System

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Thanks. I was aware of defining EP material properties; however, I was not sure if OpenStudio can feed Radiance this information. Hopefully, as you mentioned, it does. And in regard to glazing properties, you just explain to me some valuable information.

Sara_M gravatar imageSara_M ( 2015-06-29 15:21:38 -0500 )edit
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answered 2015-06-25 20:05:45 -0500

You can set reflectance in the OpenStudio application Material sub-tab. Currently we don't define the color.

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Asked: 2015-06-25 19:35:42 -0500

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Last updated: Jun 29 '15