[Quiet Man Cometh]

Just a thought, but is your front door attached to a hallway or anything? It might help to section off parts of the house with hanging sheets or curtains or something to cut down on the drafts. Pulling curtains across glass windows will also help to retain some heat, since it's an extra layer it has to get through. Make like a little foyer in front of the door, so that when you open it the air hits the sheet or curtain instead of going all the way into the house.