I've lived in my house for about a year now and I have this small room (maybe 5x6) that contains my washer and dryer. I have central air and this room does not have a vent. Also this room does not have an exhaust. Instead it just has a drop ceiling. I checked my exhaust for the gas dryer and it's fine.

I noticed a few days ago that the room was very humid. I went in the attic and noticed that the underside of my insulation located directly above the drop ceiling was black. To me this means that the previous owners have had issues with this due to the massive amount of black insulation. Since then I put our dehumidifier in the room until I can figure out how I should fix this.

I've considered a few options for fixing this issue and would like to know if anyone has had this issue and how they addressed it if they did.

1) Install flex-duct from the existing A/C ducts to the laundry room. This would cool the room and lower the moisture naturally.

2) Install an exhaust fan with a humidity sensor.

3) Keep the dehumidifier in the room.

  • 4
    Is the insulation black with dirt or black with mold? Is it feasible to leave the door to this room open? If the dryer exhaust is working properly, it should draw conditioned air into the room much as an exhaust fan would. I'm puzzled about where the humidity is coming from if the dryer exhaust is working properly.
    – bcworkz
    May 31, 2013 at 19:55
  • 2
    Is the dryer exhausting outside or into the ceiling?
    – BMitch
    May 31, 2013 at 22:26
  • 1
    The insulation is black with dirt. I can leave the door open to the room which is what I have been doing for now but my wife just wants that to be temporary. The dryer is exhausting through the wall directly behind it and out the sidewall. The exhaust is one of those flush mount runs and is only 2 feet long and about 3 inches thick. I've stopped using the dryer for the past few days and still noticed significant humidity levels with my humidity sensor and only in that room.
    – garry
    Jun 1, 2013 at 12:27
  • 3
    Is it possible your roof is leaking, causing the dirty insulation and dripping moisture into the room? Sep 12, 2013 at 2:39
  • 1
    You didn't say whether the insulation is wet, or if the ceiling under it is damp. But, if you've been running the dehumidifier for days, and not running the dryer, and the humidity level isn't dropping, then I suspect that the black stuff is mold. I'd get that stuff out of the house first, then focus on the next step.
    – getterdun
    Jan 5, 2014 at 3:47

1 Answer 1


Try installing a vent in the door, it will allow the room to breath. Make sure the exhaust from the dryer is sealed all the way around where it exists the wall, then go outside and do the same thing. Check the roof edge and make sure you aren't having water drain behind the gutter into the wall. Then climb into the attic when it rains with a big light and watch for water.

Also, get rid of that mold.. it's really bad for you.

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