Paul from Prince Edward Island needs an exhaust fan in his bathroom and wants to know where is the best place to put it.
If you go up through the roof, you will be unable to totally avoid condensation in the top of the duct that can come back into the bathroom. I would prefer to avoid going through the roof, but if you must, use a roof vent made for the job that has a collar to attach the duct to.
Through the vertical wall at the end of the attic is not a bad plan, but be sure to seal the duct air tight, to cover the duct with as much insulation as you have over the ceiling, and give it a downhill slope to drain the condensation outdoors.
My preference, whenever it is possible, is to go down through warm walls, or the back of an adjoining closet, into the basement and out from there. This allows you to use an efficient in-line fan that is quietly installed in the basement. You can even vent more than one bathroom with one Aeroflo fan.