Yes, unfortunately, at the moment we can’t select or change the orientation of the surface for exterior walls… In 2010 I participated on an ASHRAE Research Grant Project called “Development of a Reference Building Information Model (BIM) for Thermal Model Compliance Testing (RP-1468)”, which suggests improvements on current energy simulation tools to work better with BIM models. One of those suggestions was for the user to be able to determine whether to pick the exterior face of the wall, the centreline or the innerface of the wall for boundaries when exporting models.
The analysis of the results revealed, however, that for shorter wall dimensions, the percentage difference was considerably higher (i.e., wall lengths less than 40 ft.) but for longer wall dimensions, the percentage difference was less than 5%, which is considered acceptable. In that case, the orientation of the surface (innerface, outerface or centreline of the wall) was considered irrelevant, again, from an energy simulation point of view.
Give it a go with Dynamo. Whatever you come across with might be useful for energy simulation developers. Good luck!