I am trying to add a interior wall partition to an existing exterior wall (for a renovation project) The new inner wall is intended to provide insulation to the bare existing exterior wall. When I try to add this new wall, should I draw it right up against the existing wall? This will surely create problems with wall joining (and how can you have a wall created in a new phase joined to a wall created in existing phase?). Or should I leave a 2" gap between the existing and new wall? But now I am covering the existing windows in the existing wall - the new wall should of course have window openings in exact locations for existing windows? Any ideas?