We just bought a 1943 home and the inspecter says that there is no insulation in the exterior walls. The older part of the home is plaster/lath and I would like to know the best way to put insulation in (and what type?) and not have Swiss cheese for walls. We want to keep the plaster/lath walls, so sheetrocking over them is not an option. Any ideas? Can we do it from the outside and not overly damage the wood siding?