This is a question I have on my house. The bathrooms vent to the attic. Bad.
I’m going to fix this.
Should I put a vent in the roof, siding or the soffit. Does it matter.
Should I use flex pipe, rigid or is PVC OK.
Should it be insulated to prevent condensation or freezing.
Should I put the vent pipe on top or under the insulation.
Thanks
Bill
I suggest…
Roof
Rigid
Not necessarily
If it is horizontal before going through the roof, above the insulation.
But then, what do I know?
I asked my son-in-law, the roofing guy.
But then, what does he know?
This is for cold climates
The duct should vent out a gable end or the roof. Should not be in the soffit as the hot humid air may enter the roof space back up through the soffit.
Rigid ducting to reduce friction and not too long for the same reason.
Duct should be sloped to the exterior so if there is any condensation it will run out of the house and not back down the fan.
Insulate the duct to the exterior so that the hot humid air will hopefully not condense in the duct untill it exhausts to the exterior
Use a good quality exterior vent hood so hopefully it will not freeze shut in the winter.
David
Soffit, no need to add another hole in the roof
Flex is okay for bathroom exhaust venting (and cheaper)
No,
on top…
my $3.95 worth, for Sunny Climes like Mine! 
I’d rather see David’s way.
A brief study of thermal dynamics tells me the hot air exhaust into the soffit area will rise back into the attic.
Roof or gable siding what ever is the shortest route.
PVC ok, Rigid best but short flex lenght ok
Michigan - Absolutly They sell flex pipe with insulation allready on it for this purpose
On top. At least some of it will have to be above the insulation anyways and you are going to use insulated pipe.
FWIW.
After living in my new house for about two years I noticed that there didn’t seem to be any exhaust fan venting.
Upon further investigation I found that was the case. Just a fan unit covered with blown in insulation, black insualation, not pink like the rest of the attic. The sheathing 2 ft above this area was also starting to turn black.
I bought a flexible vent duct and the roof termination for it. Since it was the dead of winter I just routed the flex tube from the fan towards the center of the attic (6ft below sheathing opposed to 2ft) and planned on fininshing it that summer.
Well, you know how plans come and go, that one went. It has been seven NE Ohio summers and winters with no additional mold growth. Maybe this summer I’ll take care of it.
Bill you are in MI, condensation is an isue make sure you account for it.
Joe
