Wife and I are renting a 20'x20' Amish built log cabin that's 40 years old. This is our third summer here and we're finally trying to address how humid it gets in the warm months. We get between 60%-90% humidity most days, and mildew definitely grows on the floor, with mold growing on things that are hung against the wall or left in the dark corners. The air is also not so nice to breathe.
The cabin isn't on full electric. It has a very small solar system, but we recently ran a 500' extension cable from the main farm's power, so we have whatever can make the trickle that far available.
We've tried running a dehumidifier, which does take the humidity down (though not very fast,) while also releasing warm air into the cabin. Not really helpful for a hot summer day. Once turned off, the humidity comes right back up to normal right away.
Mostly we just air out every night and close the windows during the day, which we've learned is letting a ton of humidity in and trapping it, so now we're more leaving the windows open in the day too to air out.
Lastly, we got an air conditioning unit, which of course can't be run by our extra long extension cord setup. We run it off the generator, and were hoping that if we cooled/dehumidified the house a few hours every day it would bank us some dryness/coolness for 24-48 hours. Not so. Within a couple hours of turning off the AC, the cabin has heated up mostly back to normal and the humidity has definitely shot back up to normal.
Part of the problem is that the cabin is built on a low point in the landscape, right at the bottom of a hill. It also struggles with getting a draft for the woodstove because of this.
It was built on a fieldstone foundation that only has one point for an air exchange, this 4-5" diameter hole next to where they stuck in the main floor timber.
The only hole that was left for air to exchange is this one, at the front of the house right next to where the main floor beam was inserted. Hole is only about 4-5" wide at the widest.
This was very musky when I opened it, water literally shed off the trapdoor when I first opened it up this summer. I ran the dehumidifier in there and got it down to around 65-70% after a couple days. But of course the humidity will come right back as the floor is just the ground.
I'm a bit stumped as to what can be done besides running full power to the cabin and running AC in the summer. I have no idea what they were thinking building the cabin on top of this unventilated crawlspace that is a cold sink in the winter (uninsulated floor, mind you) and a moisture trap in the summer. I built a stick frame cabin years ago and we floated it on cinder blocks and insulated the floor, so it had none of these issues (it was also on a hill, which makes a big difference.)
My assumption would be that knocking out much of the fieldstone foundation, except for some "posts" would help a lot, including insulating the floor and maybe adding some kind of moisture barrier? Or are the logs themselves wicking in and releasing all that moisture into the air?