diffuse transmittance in OS

asked 2015-03-17 13:17:47 -0600

altamar
228 ●6

updated 2015-03-19 12:41:20 -0600

I'm modelling daylighting in OS in Win7, and we are interested in modeling diffuse windows.

For this, we need to control the values of the specular and diffuse transmittance. Is there any way to do it in OS and Win7 ?

The realese notes for OS 1.6.0 state the following:

The OSM to Radiance translation doesn’t support solar diffusing. This affects materials that have a switch in the GUI for “Solar Diffusing” when you use radiance for daylighting calculations.

Is there an alternate way to activate the solar diffusing for radiance ?

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answered 2015-03-18 10:30:27 -0600

rpg777
6980 ●6 ●15 http://openstudio.net/

updated 2015-03-18 16:26:05 -0600

EnergyPlus only supports diffusing windows in a binary way, at least from the perspective of EnergyPlus' standard materials; they are either 100% specular transmitting (i.e. clear glass) or 100% diffusing. To this extent, these are supported in OpenStudio, both on the Radiance side as well as the EnergyPlus side. You need to make a material that has the "Solar Diffusing" property set to "yes". The Radiance translator will make a "trans" material for those windows, at 100% diffuse transmittance (of the transmitted component).

Unfortunately we don't directly support materials that exhibit a mix of specular and diffuse transmittance in OpenStudio at this time.

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I have made some test and when changing solar diffusing to "Yes" in the object, there is no effect in the radiance simulation output. I found in the realese notes for OS 1.6.0 (https://github.com/NREL/OpenStudio/re...) the following: * The OSM to Radiance translation doesn’t support solar diffusing. This affects materials that have a switch in the GUI for “Solar Diffusing” when you use radiance for daylighting calculations.

Is there an alternate way to activate the solar diffusing for radiance ?

altamar ( 2015-03-19 12:39:58 -0600 )edit

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answered 2015-03-24 11:08:06 -0600

rpg777
6980 ●6 ●15 http://openstudio.net/

updated 2015-03-26 10:15:56 -0600

Support for diffusing materials in Radiance was added after the 1.6.0 release, in one of the "iteration releases". I recommend you grab the next major release (1.7.0) when it is released at the end of this month, as the support for diffuse materials in Radiance has been tested more thoroughly for this release. I will reiterate the caveat I mention in my previous answer, as well: the Radiance diffuse material support is all-or-nothing; if you have a material in the construction that is SolarDiffusing = YES, the construction will transmit 100% of the transmitted component of visible light in a Lambertian manner.

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