I was not sure how to catagorize this problem:

The issue is that we have condensation building up in the ceiling vent in our bathrooms. That condensation is filling up the light fixture, soaking into the ceiling board and dripping down onto the floor.

I realize that the condensation is form the cold air coming down the vent tubing and then mixing with the warm air. I have improve the ceiling air flow by cleaning and enlarging the sofit vents. That seems to have corrected our master bath condition. However, our guest bath sill have water dripping from the ceiling light/vent fixture. I am at a loss on how to correct this.

Some other facts:

- The guest bath is rarely used, so using a shower (humidity) is not a factor
- The vent hose (3") runs from the bath ceiling vent/light fixture up to the roof cap, probably 15 to 20 fee sloping up to the roof.
- I have ruled out rain or snow entering the cap, this also happens with no precip outside
- Other homes in the neighborhood of the same design (ranch), and no problems reported.

Is this a matter of a poor fixture design? Should there be some in line gate in the 3" flex tubing? I'm at a loss on ideas!

Thanks

Bob

Do you have a humidfier in your home?

Yes. It is set to 45 to 50% humidity.. I have a hygrometer.

Most fan enclosures like yours have a flap damper in the outlet to control this. Check to see if it is stuck open or missing.

Lower your humidity and the moisture problem should go away. Checking the little damper door as suggested above is also a good idea.

The moisture problem you are having can be cause by many problems.

To high moisture level in the home. Not only will this cause a problem like you have but it can also cause mold and mildew in places you cannot see until it is too late.

Next is a cold area. Moisture will migrate or collect at areas that can be considered cold. The water vapor turns into condensation like you sometimes might see on the older style windows. If too much moisture and to cold an area it can actually freeze like I have seen it do on old single pane windows.

I believe your moisture level is too high in your home to start with. While it is good to have some added moisture in the winter time too much can cause a bad situation.

Good controls for humidifiers have a outside control section also. This allows the humidistat to adjust the moisture level along with the outside temperature always assuring a perfect amount of humidity. Most people do not have this kind of a control because they cost more than the standard control that comes with the humidifier.




Too Much Humidity

Your skin often feels clammy, sweaty or sticky.
Musty-smelling odors are invading your living space.
Wood floors, trim or wood furniture is warping or rotting, paint is peeling.
Condensation, frost or ice have formed on the inside surface of your windows. Water pipes are "sweating".
Damp spots, or worse, mold and mildew, have formed on ceilings or walls.
Your allergies or asthma have gotten worse due to the growth of mold, mildew and dust mites.
Your house is a breeding ground for termites, cockroaches and other pests.
See attached chart for proper humidity levels at what outdoor temperature.As the ouside temp drops so should the humidity lever. This helps to prevent the problem you are having.

I am not an expert however I read that the vent pipe should be insulated in cold climates to prevent condensation. I used self stick foam from Lowe's.