Code requires All Exterior walls and ceilings are Insulated. Interior walls are not unless you are trying to block out sound like in bathrooms.
So the way I do things is if there is a wall seperating a noisy room from a bedroom I insulate that wall,all bathroom walls,All topfloor ceilings,perimeter crawlspace walls,all exterior walls and I have even insulated walls and closets if there is a bedroom on the otherside of it. Now some may say this is over kill but I have had many thanks for doing this over the years. In your case just make sure theres insulation and Vapour Barrier in any ourside walls the rest is just choice.
Hope this helps.