I've been having humidity issues for the past few years in the near building:
The unit was originally built as a garage, and some time before I purchased the property it was converted to living space. The unit is built on a concrete slab. The ground is (I think) pretty wet. There are no soffets and no ridge vent.
The interior is divided into two spaces. Here is the "front" living area:
This is behind the windows in the first photo. There is a wall running the length of the room. Behind the wall is a utility room. (Accessed from the door off the patio in the first picture.).
As you see, the living space has a cathedral ceiling. The utility room behind the wall has an attic space -- the vent to the left of the room in the first photo opens into the attic above the utility room. There is a whole house fan venting out of the attic.
A few years back, I had an insulator come in to look at space because the insulation in the attic was falling apart.
He recommended closing off the vent from the living space to the attic to keep the hot air from escaping during the winter, which we did with a piece of rigid foam insulation.
The problem is that the next summer I started experience bad humidity problems in the room. The dry wall tape is cracking up in the corner of the cathedral ceiling. There is mildew forming above those beams. And there is what appear to be mildew stains forming around the arch window (as if humid air is coming out from little gaps where the molding meets the drywall):
You can see from the bottom picture, that those beams are just the ceiling joists sticking through the sheet rock of the ceiling. That gap is open to (I assume) the space between the sheet rock and the underside of roof (plywood, I'm guessing).
There is a green plastic vapor barrier under the laminate flooring in the living space. (again, I assume it's a vapor barrier, what it really is, I don't know.) The floor of the utility room just has vinyl tile over concrete -- no barrier. Behind the walls of the living space is another plastic sheet (clear, but with rips) and fiberglass insulation -- although with lots of gaps.
Thanks for reading this far.
I think what was supposed to happen is that the hot, humid air building up at the top of the cathedral ceiling was going up into the roof where the joists went through, and from there, flowing to the left, into the attic space and out through the whole house fan. I think that when the insulator blocked off the vent, he also added insulation to close off the space at the top of the attic leading under the roof. You can kind of see that up at the top of this picture (above the netting):
I think this is preventing the humid air from venting out of the living space. It travels up and tries to get out where the joists are, but gets trapped there.
So, what do I do?
I've opened up that vent during the summer, which seems to have helped a bit.
I could remove the batting from in the attic where it's blocking the gaps to the space over the cathedral ceiling. But for all I know, they should be there.
I thought about "plugging" those holes where the joists go through the ceiling. But I don't see what good that will do.
I'm not sure what I can do about humidity escaping from behind the arch window -- except caulking the gap. But it may be worse to trap the humidity in the wall.
Other than putting down a vapor barrier in the utility room, I'm not sure what I can do to prevent humidity from getting into the room.
Sooooo. Any suggestions?
Thanks. I'd appreciate any help. Maybe someone can confirm/explain how this room was supposed to have been vented/insulated.
I thought I might be able to get a skylight with a vent, but apparently those don't exist.