The ceiling fan in my bathroom has started dripping now that the colder weather has arrived. I suspect that as the warm moist air from the bathroom passes through the ductwork in the colder attic, condensation occurs and the water runs back down through the fan. Do I install a damper, insulate the ductwork, or route the ductwork so that any condensed moisture flows away from the fan to somewhere else?
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Insulate the ductwork and slope it downward to the vent (if horizontal) so that water runs out.
You can replace flex duct with insulated flex duct, but metal with wrapped insulation is better and tougher.
It should have a damper either way, but you will still get condensation with a damper and uninsulated duct.
Use insulated flex duct, slope it so that the majority of the run is away from the fan to the vent for drainage (if possible) and replace the wall switch with a 15 minute spring-wound timer switch so that the fan runs long enough to remove moisture after you have left the bathroom.
Do you insulate over the actual fan housing? Or does that contravene electrical codes for insulating around things like lights in ceilings?
When ever I install a fan/light unit with exposure to cold space I insulate around and over the unit and I insulate the duct to the room vent or side wall vent. I wouldn't worry about heat in a fan unit .
AAARRRGGG! Why do people run ductwork in unconditioned spaces?
You don't say whether the fan is ducted through the roof or down to a soffit.
If through the roof, you're in trouble. You'll have to reroute the duct to another outlet that allows drainage, as well as inuslating the duct.
A second storey bath fan should be installed in a dropped soffit so that the ductwork stays within the insulated space. Perhaps this is an option?
Ideally all exhaust ductwork goes into a wall and drops at least 3' before exiting so that backsiphoning of cold air is suppressed and so that any condensation can drain downward and out.
Solar & Super-Insulated Healthy Homes
never vent through the soffit, or sidewall immediately below the soffit, the "air-oh-dynamincs" will draw the most air through the soffit venting into the attic. I have seen this happen on several occassions, the spring thaw should be a relief, not a nasty surprise ..
never vent through the soffit
Well that's a bold statement. As in most things, never say never.
I would agree with the statement if you added: "when there are soffit intake vents or very loose trim which can allow the moisture to get sucked up into the attic."
But if neither of those are the case, then venting a bath fan through a soffit can be a better alternative than venting through the roof, which creates an additional roof penetration and can cause the very problem which the OP complains of - dripping fan.Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
when you get called at 3 in then morning that the bedroom cieling has fallen down and every thing is soaked you'ld give the same advise. Almost all newer homes have vented al soffit these days, and even if they don't take a look at what happens to warm air vented through the soffit on a cold day. There is a circular vortex that forms under the soffits trapping the air. If the vapour doesn't get into the attic it will condense of the soffit, or wall, I have also seen spalled brick ..
Almost all newer homes have vented al soffit these days
Maybe up your way, but here in Vermont houses are still built of wood.
And "NEVER" is used only by those who don't understand the spectrum of options and the relative positives and negatives of each.Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes