Tip: don't use PixelCounting in combination with Transmittance Schedule

marctavenier · September 14, 2021, 9:21am

Hi all,

Just thought I’d post the following, which I found out after a lot of trouble shooting, to save someone having to do the same

When using HB shades with an EP Transmittance Schedule, make sure to also use PolygonClipping as a Calculation method in the HB Shadow Calculation. When using PixelCounting (which I set up at first because of the high number of shading surfaces present), it won’t account for any transmittance and see the surfaces as fully opaque throughout the year.

Kind regards,
Marc

chris · September 14, 2021, 12:29pm

This is good to know, @marctavenier . It sounds like this is a bug in EnergyPlus or it’s at least not the expected behavior. Did you open up an issue about this on the EnergyPlus GitHub so that one of the E+ developers could confirm?

marctavenier · September 14, 2021, 12:57pm

I did now!

github.com/NREL/EnergyPlus

Unexpected behavior when using shading surfaces with transmittance schedule and PixelCounting

opened 12:56PM - 14 Sep 21 UTC

marctavenier

Issue overview -------------- When using shading surfaces with a transmittance… schedule and the PixelCounting shading calculation method, the transmittance schedule seems to be ignored and all surfaces are made fully opaque. To me this seems to be a bug or at least unexpected behavior. When using PolygonClipping the transmittance schedule works as expected. ### Details Some additional details for this issue: - Windows 10 - EnergyPlus 9.5 via OpenStudio 3.2.0 via Ladybug Tools 1.3.0 in Grasshopper. - As indicated on the Ladybug Tools Discourse [here](https://discourse.ladybug.tools/t/tip-dont-use-pixelcounting-in-combination-with-transmittance-schedule/15871)