Insulation job: from the inside or the outside?
Hi to everyone, thanks in advance for helping me out on this one.
I bought an old house 2 years ago and I started renovating it last year. The house was built in 1941, which is about the oldest houses you can get in my area of northern Quebec. The original insulation is sawdust, and it has become compressed in the lower 4 feet of the walls, leaving the rest of the walls with no insulation.
I have an evaluation from a governemental energy agency that suggests somes things to be done in priority to save energy, and the best way to do them. They suggest I get rid of the sawdust and fill the walls with projected polyurethane by the outside (which I cannot do for financial reasons), or let the sawdust in place and project polyurethane above it (which would be fine for me). Then, complete the insulation with projected polyurethane on the outside onf the house, or polyisocyanurate sheets.
Before getting the report, my local renovation center suggested I placed the polyisocyanurate sheets directly on the outside wall, without concerning myself with the inner walls. It cost much, much, much less than putting projected polyurethane in the walls.
I phoned the inspector and talked to him about that, and here is what he told me. He said that I need to put an insulation inside the walls to cut the vapor from entering the sawdust and the wood structure. If I only put insulation on the outside, humidity is sure to find its way inside my walls, creating a mold problem in no time. That's the reason why he suggested to fill up the walls before adding outside insulation. My local renovation center says it's overkill.
I know next to nothing about insulation, and now I think I am more mixed-up than ever. If someone in here is experienced in this aspect of renovating, I would be immensely grateful for your opinion on the matter.
THanks a lot