I am getting ready to renovate an old two-story house. I'm not sure what I should do about insulation. The upstairs has 2x4 studs with 3 1/2" paper-backed fibre insulation. There is a layer of 1 inch lumber and then drywall on the inside. The outside has 2 layers of 1 inch lumber. The downstairs floor is the same but has sawdust in the wall instead of paper-backed fibre. I would sooner spend more money now on insulating properly but I don't want to over-spend. What are my options? Blown-in? Styro sheathing? A combination? Please let me know what you think.
Answer:
Once there is any amount of insulation in a wall you cannot blow in more. I would get rid of the sawdust, leave all the other insulation in place and if there is a vapour barrier question at all, I would line the perimeter walls and uppermost ceiling with 6mm poly before applying drywall over the whole thing. Where you have sawdust right now, you want to add more fibre bats but you should try to stay away from the rigid foams because you can get rigid fibre for a better price and get just as good value out of it.
