Material:RoofVegetation (EnergyPlus) - unaffected by shadow calculations?

asked 2020-10-19 22:58:09 -0500

Adam's avatar

updated 2020-10-24 11:26:42 -0500

Hi All,

Is the RoofVegetation Material in Energy Plus unaffected by shadow calculations? If not, how does one get shadows to affect calculations?

I have setup a relatively simple simulation comparing outdoor surface temperatures of asphalt, concrete and grass using Rhino>Grasshopper>Honeybee>Energyplus.

The grass is represented by the RoofVegetation material. Disregarding discrepancies between the anticipated temperature differences of the materials and those generated by the simulation - a seemingly stranger issue seems to be that, unlike the other materials I have used, the RoofVegetation material is seemingly unaffected by context shade.

Is this a known issue, or perhaps something missing from my script?

Unfortunately I do not have enough points to upload here but you can find an image of the issue and my grasshopper script on the Ladybug forums here: Ladybug thread

Any advice woill be greatly appreciated.

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@Adam welcome to Unmet Hours!

Is that image in your Ladybug thread the result of breaking up each surface (asphalt, concrete, grass) into a grid of "sub-surfaces"? I ask because if you define a surface in EnergyPlus, the surface temperature output is calculated for the entire area.

Aaron Boranian's avatar Aaron Boranian  ( 2020-10-20 07:37:42 -0500 )edit

Either way, I would suggest not using surface temperature outputs to confirm the impact of shadow calculations. EnergyPlus has a Surface Outside Face Sunlit Fraction output and Surface Outside Face Sunlit Area output that would likely work better to analyze shadows on adjacent surfaces.

Aaron Boranian's avatar Aaron Boranian  ( 2020-10-20 07:40:07 -0500 )edit

Thanks for the reply and welcome Aaron.

Adam's avatar Adam  ( 2020-10-20 18:27:31 -0500 )edit

Yes, the image is of a 9x9 (81) grid of adjacent sub-surfaces with each material applied to 3 rows (27) of these sub-surfaces. I am attempting to calculate surface temperature variations in shaded versus non-shaded areas using different surface materials, vegetation being one of them. In the example, the asphalt and concrete sub-surfaces are successfully calculated independently, with temperatures of sub-surfaces in the shade of the context sphere attenuated. The temperatures of the 27 RoofVegetation surfaces, however, are being calculated uniformly with no attenuation from the sphere's shadow

Adam's avatar Adam  ( 2020-10-20 18:31:54 -0500 )edit

Which is the bit I find strange. Why are the surface temperatures of the RoofVegetation material unaffected by shade?

Adam's avatar Adam  ( 2020-10-20 18:39:30 -0500 )edit