I purchased a log home last year and would like some advice on how to improve the insulation. I know, this question has been asked a few times before but I have some specific concerns that I couldn't find straight answers to.
I'm in norther Michigan, climate zone 6. The home is pretty large, 4,000 sq ft two story with cathedral ceilings, loft with 2 bedrooms upstairs and 2 on main floor.. It's a butt-and-pass 6X6 milled square logs, chinked, on a block foundation with crawl space.The roof is spray foamed with closed cell about 4-5 inches thick and the foundation in the crawl space is also spray foamed. Crawl space has a vapor barrier over the dirt floor but its not sealed to the spray foam (foam done first) and its also not taped at the seams. This winter we were able to keep the main room of the house fairly comfortable using an interior wood stove and about 450 gal of propane in the back up furnace. The first bedrooms stay pretty chilly unless we use a space heater at night.
This spring I'm going to have a blower door test done and a general energy audit to help seal any leaks. Im also planning to update the exterior doors and possible the windows this year. Other than leaks, my main concern are the small 6 inch logs used for construction. I'm going to seal the exterior checks and re-do some failing chinking. The guy who built this did not use gaskets or any caulk between the stacks (among lots other things he did a bad job on that I found after buying and the inspector never mentioned). My thoughts, like others have mentioned, is to build a second stud wall inside to insulate the exterior log walls and cover with either dry wall or tongue and groove knotty pine. I know it would be best to insulate from the outside with foam boards and a house wrap then siding but I'd prefer an interior approach unless its no other option.
My main question here is if I go ahead and do the second interior wall what issues do I need to worry about in terms of vapor and potential log rot? I have noticed a few areas with water staining on the interior walls, these can be tracked to exterior checks or corner chink that needs addressing. I was thinking about a flash and bat with closed cell foam on the logs and rock wool over top but the potential for water not being able to escape should it get inside and log rot has me rethinking. What would be a good option? Rigid foam directly to walls with furring strips for wall finish material v.s. 1X4 furring strips and foam board over top leaving a small air space between foam and logs v.s stud wall with rock wool batting? My gut tells me stud a wall then 2x4 thickness rock wool would be a good compromise of R value and still letting any potential moisture sneaking in/out to not be trapped. I could even turn the studs or use 2x3 for the uprights to minimize conduction with the log wall.
Would adding this extra insulation to just the lower floor bedrooms make much of a difference or is it not worth it unless you do the whole house? The main room and loft get pretty warm from the wood stove but as I stated before, the bedrooms on first floor are the coldest in the house. Also considering radiant floor heat in the bedrooms but that's another story.
Selling/moving is not really an option but if this house gets to be much more of a head ache than it already is I may be investing in a bulldozer . . .
I know this is a lengthy post but I'd really appreciate any help. Ive seen other kit log home companies offer similar interior insulation options so maybe someone who has such a set up can reply with any issues of log rot or moisture.