ONETIME- Open vents: And get yourself a vapor barrier
One time, I had a call from somebody in Wintergreen who was having trouble with some doors closing. So I went up and looked at it, and he had some cracks in the sheetrock around the door frames and the sliding doors wouldn't work properly. So I went under the house, which was built on a crawlspace, and the floor joists ran across these beams which were supported by posts.
And when I opened up the crawlspace and went in, it was like going into a cave. The insulation was falling down from between the floor joists– water was just dripping off of it. There was no vapor barrier down under the house.
The tallest section was about 4 1/2 feet tall, and it went down to about twelve inches off the ground on the uphill side. And I started looking around and the beams that were supporting the floor joists were like triple 2 x 8s, and I could just take my hand and break off chunks of these beams, and it was the same with the 2 x 8s that were the floor joists.
And the house was only thirteen years old.
The entire floor support system of the house was rotting away, and that was what was causing all of the doors to fall in and not work properly because the whole house was about to collapse. Water was oozing through the rocks on the mountain into the crawlspace. He kept the vents closed because he was an absentee owner who only lived there during skiing season and he never went under the house, so it had basically been doing that since the house was built.
So we had to go back in and replace everything underneath: jack the house up, scab on new floor joists, replace all the beams and posts, tear out all the old insulation, put a vapor barrier down, and added an exhaust fan system on a humidistat to remove moisture down there.
Where the posts came up against the bottom side of the triple 2 x 8s, you could see the 2 x 8s were kind of sagging on each side of the posts, so it hadn't completely rotted through and it had some amount of support. In a couple more years, the thing would have just collapsed.
This is a cautionary tale for homeowners: keep your vents open in the summertime, closed in the wintertime, and make sure you have vapor barriers down in your crawlspace, because moisture can get underneath there and really do a number on your house.
It's surprising how much moisture comes up just through the ground like in a dirt crawlspace: you can put a layer of plastic down and in fifteen minutes you'll see moisture on the bottom of it.