Hey @molly ,
The unreliable nature of working with curved geometry in the Legacy plugin can be calked up to the fact that the Rhino “Offset Curve on Surface” method that’s used to produce the window doesn’t always return a result that yields a valid window surface. The philosophy that we took in the LBT plugin that was released last week handles cases of single-curvature MUCH more cleanly and results in much faster energy simulations since you need a lot fewer polygons to represent the curvature:
If you have to build an energy model starting from curved geometry, I would generally recommend using the LBT plugin over legacy since you can get a lot more control over how the geometry gets planarized for EnergyPlus in the new plugin.