[Bldg-sim] Modeling of Solar Tubes in Design Builder

Lars O. Grobe grobe at gmx.net
Tue Feb 19 14:40:49 PST 2013

Hi Sheelam,

probably this is not possible without tweaking. As far as I am aware,
Design Builder uses the standard backwards algorithm of Radiance. That
one is not really made for typical solar tubes, if you want to consider
direct sun and you have no diffuser on top of the tube. If you would run
your Radiance simulations directly, you could either use a sky where the
direct sun contribution would be spread over a wider solid angle (see
Tregenza's sky subdivision scheme) or apply extensions such as the
Photon Map. I doubt that these are available in Design Builder (though I
do not really know this for sure). If you need a front end, you can have
a look at Daysim, which includes the Photon Map and also supports the
daylight coefficient method using Tregenza and higher resolution sky models.

I would recommend a look at the Radiance workshop presentation of the
recent years, which are all available at www.radiance-online.org.

Cheers, Lars.

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