Just a for what it's worth post. Lots of posts here about humidifiers. After 27 years burning wood in this joint, last year I had a serious health hit and suspected the trigger was low humidity in the place, 20 percent when burning, and got a lot of relief by firing off several humidifiers and keeping the place around 40 percent during the heating season. Continued with it this year. Today i went up to check the flue and coming down I passed the gable vent and caught the distinctive smell of mold coming out of it. Went down and went up in the attic. Entire place covered in mold. Underside of sheathing and rafters. This ain't gonna be easy or cheap. I was up there just six months ago and it was not there. Only change in 27 years was the humidifiers. And I have spent a while on the web finding a lot of people that had the same thing happen with humidifiers. Yeah, it has to be getting up there somewhere but the heat going upstairs is carrying the humidity with it, which I was loving. But now to find how it gets in the attic. Just sayin, check those attics if you use these things.