Thanks for the responses, guys. Appreciate your concerns.
After running the dehumidifier an additional 3 hours, the total water sucked out of the room was around 1 gallon. To be fair, two showers were taken during this time as well. But this morning, the bedroom windows were dry - in the past they've been covered in mist. And the room feels noticably dryer. So the dehumidifier is doing the trick for now...
To address some points:
- I do not have forced air - it's baseboard heating (aka heated water heat.) But that's supposed to be a dryer heat anyway.
- I do not have central air either (shocking in this modern world!) I do have a window A/C unit that I put in my bedroom every year - this year, we used it exactly ONCE the whole summer. Most of time, we have a small two-fan window fan unit that pulls in fresh air from outside. But obviously that fan isn't strong enough to push all the humid air out.
- The likelyhood of the issue being a leak in the pipes is minimal at best - there are no pipes running in the walls of the bedroom. See diagram. Although the roof is 20+ years old, it doesn't leak. That said, I will poke around the room to see if there's a source of water that I'm not aware of. Fortunately, underneath the room is my garage, so I can have easy access there, and above the room is the attic. (It's a bi-level house, BTW).
- I have a small apartment downstairs on the other side of the house - and I have noticed that it the air is a little stale there if it is closed up for some time.
- The house itself is built half-way up a hill, so there is no standing water that I know of, unless runoff from the hill is settling around the foundation. But there's an easement running through my property uphill from the house that is for water run-off. At it's closest point, that pipe is 30 feet away from the house.
- It has been a wetter year in terms of average annual rainfall in our area - so that may also be a contributting factor.
- Per the diagram, the mold is really growing alot in the area just above the door between the bedroom and the bath. The bathroom has been painted with mold-resistent paint which keeps the mold level significantly down. The walls of the bedroom are painted with semi-gloss paint - and there's no mold there either. But the bedroom ceiling is painted in a flat paint - which is more prone to mold, if I'm not mistaken. The ac unit is in the bedroom window closest to the bath, while the fan we usually run is in the other bedroom window.
- Before we had our lovely pet bunny, the bedroom door would remain open for most of the day, which would help air out the room. I think I may buy a baby gate for the door so it can stay open -- while that may bring up the humidity level in the rest of the house a little - I don't think it will lead to bigger problems, since the air to humidity ratio will be more favorable.
- I am also hoping to get the bathroom fan installed ASAP - will look into getting a higher end/quieter unit.
- I do believe the main issue that is causing the mold buildup is lack of ventilation.
Thanks again for the comments and suggestions. There's always good info here!
-Zoltan.