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Leaky Attic Exhaust FansI had an attic exhaust that appeared to periodically leak. It didn't leak every time it rained and I could figure out what was causing it to leak for quite some time. I could have a downpour of rain, check on the leak, and it wouldn't leak. I thought about it and it seemed so random that it would leak, I wondered if it only leaked in the hardest rains, or maybe when the wind blew hard or in some odd direction, but I couldn't catch it leaking. I occasionally see evidence that it had leaked when I went to the attic to store or retrieve items stored there.
Then one day it was raining, not particularly hard and it wasn't windy, but it was leaking. It was running at the time because it was the afternoon and it seemed to spit a large drop of water about every two or three seconds into the air. The drop fell at about 30 degree angle from the bottom edge of the upright tube that the fan was in and landed a couple of feet from where became airborne. The landing position was fairly constant so the point that got wet was under the higher side of the roof from where the fan was.
Once I passed by the fan a couple of times this day, I realized that the water was being pulled in through the seams of the fan housing due to the slight vacuumed that the fan creates as it runs. This meant that the only time there was enough water leaking to attempt to trace a leak was when the fan was running and there was a steady rainfall. The capillary action of the seams coupled with a slight vacuum is more than adequate force to pull water up through the seams and cause a leak. In fact since these fan housings are generally always slanted with the roof line, this caused the water to collect at the lower edge of the opening into the large water drops that seemed to be spitting into the air from the fan.
I immediately ended up on the roof, when enough time had passed for the roof and fan to dry out, with a roof sealer to seal all of the seams in the fan housing. One would think that the fan manufacturer would seal the seams of their fans, but it appears that they were counting on gravity to prevent any leakage. The evidently didn't account for the fact that there would be a slight vacuumed on the seams when they designed the fan, and the seams definitely had no sealer added during the manufacturing process.
So, if you have a ceiling fan, you should check to see that the seams have been sealed by the installer, and either get the installer to seal the seams or get a tube of roof leak product and seal it yourself. It's messy to do it yourself, but it's better than having a leaky place in your roof that will eventually cause enough damage that you will be faced with the cost of repairs to your roof or ceilings.
If you are the manufacturer of this type appliance, attic fans or vents, you should be aware of this problem, and be diligent during your manufacturing process and put a seam sealer in or over the fan housing seams. The alternative for manufactures is that eventually you may end up facing a class action law suit due the damage that your products have caused to each and every roof that contains one of your fans unless you properly address this issue.