I bought my house 4 years ago and I had always noticed that the bathroom exhaust fan just wasn't doing its job properly. I figured that the thing is old; it worked but not as efficiently as it should have. I endured with it until last week when the motor went. I went to remove it so I could see what size ductwork was there. Well, you guessed it! No duct work. Well, there was about a 3 ft. duct attached, but it was vented right into the space between the ceiling and the roof -- a duct to nowhere! I guess I took it for granted that when I turned on the switch and the fan went on, then the exhaust was going out of the house.

So, I need to make an outlet for a new duct but not sure whether it should be on the roof (my roof is flat on top and I've heard that poking holes in a flat roof really isn't a good idea.) Or should it go through the side wall of the house. In this spot, there is an overhang with shingles and plywood underneath. It would be about 3 feet if I go out the side of the house whereas it would be about 2 feet to go straight up and out of the roof. Can anyone tell me which way is the better way to go? I'm good with all the wiring and I have all the tools; just not sure what the best location is for the vent. Any tips appreciated! Thanks!

The best venting would be through the wall, second best into the eave and the worst would be poking that hole in the flat roof. Bathroom exhaust air is damp and is best vented directly out of the building through the wall. I have seen many bath vents that dump into the soffit but this can lead to rot and a damp attic which can frost in the winter.

Make sure a check valve is installed in the exhaust line.

All of the bathroom fans I have installed have a flapper box which is installed right on the fan housing. It is a necessity