Gas and Oil Home Heating Furnaces - bathroom venting

i recently added a vent in the ceiling of my bathroom.i connected a dryer duct material to the exhaust on the vent and clamped it.i then ran the duct through the attic to a roof turbine.i took a square piece of plywood and attached it between two roof rafters directly under the turbine.i then cut a hole in the plywood and connected the duct to a tailpiece that is screwed to the plywood and clamped the duct material to the tailpiece.is this a good idea?do i need to wrap insulation around duct material?i don't want to install a roof vent.do you have any ideas,suggestions or will my initial plan work.thanks,jason

May be a problem if your attic goes below freezing.The warm moist air from the bathroom will probably form frost.When the attic goes above 32 degrees the accumalated frost will then drip down and follow the vent piping to the ceiling below.PDF

I live in Wisconsin where it can get very cold and my bathroom exhaust fan uninsulated ducting is ran vertical through the attic and is terminated in an existing roof vent. As stated by PDF, you will get freezing condensation, but it will be on the inside of the duct. When the attic temp is above freezing, the thawing condensate will run to the lowest point. In my case, I have on occasion had water drip from my exhaust fan after the attic warmed up following a cold spell. Insulating the duct will allow more of the moist air to be vented before it condenses and help reduce the build up of frozen condensate.