Do I model the inner, outer or center line of walls?

When I model room surfaces in Honeybee, the walls have no thickness; so when I draw a 2D wall, am I modelling the interior, exterior or center line of the wall? So far, I have generally modelled the outer boundary for exterior walls and tried to model the center line for interior walls.

what kind of analysis you are going to do?
for daylight simulation, you should model the wall with thickness.
for energy simulation, I usally use inner boundary for exterior walls, and for interior walls, of course center line is best, but side line is also can be used.