I have been working on sealing my Attic and third floor in preparation for insulating the Attic. It is hard to imangian that after over 100 years that no insulation has been installed in this house. With the increase of fuel costs I have to seal up the house and insulate. The big question is what type of insulation should I use in the walls? The make up of the walls is Clapboard sidling, 1" x 12" planks, 2 x 6 studs, then 1" by 12" planks and then lath and plaster. I am removing the plaster room by room and replacing with wall board due to the plaster is like powder. It is impossible to insulate the wall cavities with fiberglass bats because of the inside planking.