Bathroom Leak Around Ventilation Fan

I have a leak question that I'm a little stumped over. We moved into our house in September of 2005 and noticed a repaired patch of ceiling near the bathroom ventilation fan. I ignored it as it was not leaking at the time. For the first couple of months there were no problems. One day we noticed a small amount of water dripping out of the ventilation fan's cover. Not much water - just about one drop every 3 seconds for about two minutes - then gone. I would wipe of the cover, turn the fan on and that was it. We noticed that this happens the morning after a light snowfall - never rain. Today we noticed that the repaired part of the ceiling if cracking - with water spots. I went into the attic and discovered that the ventilation fan's tubing is connected to the fan right above where the ceiling leak is. I did not see any leaks in the roof, leaks around the area where the vent tube exits the roof, or even any water on the outside of the vent tube.

Am I right to assume that water is somehow getting into the ventilation tube? Can or does snow blow into there somehow? Is there a better top-piece for the vent tube that I can purchase? Am I way off and this is some other problem.

No showers or anything were taken around the time of the leaks.

Thanks.

 

What you are describing appears to be condensation. The exhaust tube in the attic is not insulated, and as the warm & moist air from the bathroom is blown up the exhaust, it condenses on the tube and runs down the walls of the tube. Depending on how well the tube is joined to the fan, there may be accumulation of water at the base of the exhaust that is leaking out.

If you insulate the exhaust tube, then dew point will be outside - so the vapour will condense outside the vent, not in the exhaust tube.

 

Thank you - is there a specific product I should be looking for to insulate this? It is a black PVC pipe about 4 to 5 feet long.

 

You want the same amount of insulation around your pipe as you have in your ceiling. Say (for example) you have R-30 in your ceiling - you should have a similar amount around your pipe. There are products made of flexible closed-foam plastic for insulating pipes, and some of them come in sheets about 1/4 to 1/2 inch thick. Check the R-value per inch for the product, then wrap enough of it around the pipe to get the insulation value. Alernatively, you can use pink fiberglas insulation and wrap it loosely around the pipe - but be careful not to compress it as this will reduce the R-value.

 

Thanks very much.