Well we’ve decided to tear out the exterior walls of the old house. We had been on the fence about this, thinking it might be easiest to leave the existing interior mishmash of plaster/lath and drywall and just blow in insulation behind it. On further consideration we’ve decided to brave the cold and start tearing it all out down to the sheathing since we didn’t really know what was underneath that might get in the way of blown-in. Good thing, too. For some reason it was deemed wise, a century and a half ago, to fill in the space above the doors and windows with BRICK! Why? We’ve noticed that the gables up in the attic are also filled with brickwork. Weird. Now that really would have gotten in in the way of the blown-in. Found a pine cone and a six of hearts behind the walls too. Now we’ll keep working at the gutting and start insulating. After that drywall. Our current thinking is to use blueboard plaster veneer drywalling. This is a new type of drywall that is covered with a thin layer of plaster which gives a surface more like the original plaster on lath.