Hi Chris,
I was testing out the “HB Vegetation Material” but had a few issues. The problems I came across were from trying to use it as a ground material rather than roof material so maybe it’s just that I’m using it for the wrong puprose but i’ll post anyway in case it’s useful for others.
First is that if I plug the Vegetation material straight into the Ground Component it comes up with an error because there’s no roughness value (see screenshot 1)
Since the Ground component didn’t work I built the ground zone from faces and assigned the Vegetation material to the Roof of the ground zone but when I run it through energyplus, shading context isn’t recognised (see screenshot 2&3). I’ve checked boundary condition is Outdoor for the roof and tried adding another soil layer underneath (as suggested in this post Surface Outdoor Temperatures - RoofVegetation (Grass) EP construction not affected by context shade? - #2 by chris)