I've just purchased an 1830-1860's farm house in Montpelier VT,("needs work" is an understatement) and I think I need to start by replacing the roof. My question is how to insulate? It's been suggested I should be concerned about condesation. The roof boards look tight enough so that with heavy felt, plywood shouldn't be needed, and in fact, no one has given me an estimate that includes plywood. But, back to insulation. Should I have the roofer put down 1 1/2 inch styrofoam from roof edge up to beyond ceiling height on second floor, fill the rest with 2x4s and then lay plywood over everything, felt and then architectural shingles... or should I try to insulate from within, and rip out walls to insulate and then blow in insulation on top of 2nd floor ceiling? Seems messy to start ripping out walls....but it also seems kind of important to put some sort of insulation there to prevent condensation. Am also probably going to ask for a ridge vent so the house can breathe a bit. Am I going overboard to think about putting a layer of insulation ON the old roof boards and under the new shingles?
Thanks for any advice from folks who know...