Vent bathroom fan to ridge vent by constructing an adapter at ridge?

I've seen plenty of postings that one should not vent bathroom fans to soffit or ridge vents. I completely agree about not using the soffits. But how about using some blue foam, or other material, and making some sort of 4" round pipe to ridge vent adapter. Think of all the sheet metal HVAC adapters at home centers. But I'm thinking of just fabricating something that custom fits my roof/ridge vent at one end and a 4" round opening at other end. I can purchase a 4" sheetmetal colar to make the round opening in the foam. This would force 99% of the moist bathroom air directly out a portion of the ridge. The foam adapter would protect the roof sheathing from moisture, plus it's easily built on site.
Downfalls? reduced ridge ventilation for the attic - but I doubt enough to have any impact
Appreciate any comments...
Thanks!
-Mike
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Mike wrote:

I don't think I would want to do it. However if you insist remember that ridge vent is not open and has a fairly high resistance at the air speeds a vent fan would be using so you would guess you would need a few feet of vent in order to get something close to the efficiency of a dedicated vent.
I might add that most ridge vents I have seen have exposed wood surfaces and that warm moist air would damage the wood deck. You would need to make some accommodation for that as well.
--
Joseph Meehan

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Do you maybe have a sealed off gable vent you can convert to vent the bathroom. Cutting a hole in the roof (for a standard vent stack) sounds like less work than what you propose.
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Joseph Meehan wrote:

I had not thought of the air flow resistance of a typical ridge vent - good point! Maybe that is why many posts on this topic do not recommend the somewhat common practice of simply stapling/hanging the fan's exhaust pipe near the ridge vent.
I was just hoping to avoid putting a hole thru the roof to install a typical roof cap. I'm very handy, but I stay off the roof these days :) Guess I'll pay a carpenter to go up and do it :) Another option, if I want to do the work, would be to install a wall vent. At least I can get to that from the outside with a ladder. Easier for me to inspect/repair should it ever leak too...
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There is also a vent damper that exits thru and down from the soffit which puts it in easy reach and well protected.
Mike wrote:

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I had a bath fan mounted to a attic vent (the 12" square kind with the 6" hole). THis worked for several years but then I found that I burned out the fan motor. I replaced the fan motor and after a few years burned that one out as well.
I investigated the whole system and found that the attic vent had a screen inside it that is used to keep the bugs etc out. Over the years this screen became clogged with lint etc from the bathroom. So the fan motor was working extra hard to push the air through the clogged screen. I also found that the flex duct pipe that I had going from the bath fan to the attic vent did not have insulation etc on it so the moist air would condensate in the duct and actually run back into the fan and eventually dripping on the bathroom floor.
I just replaced the whole system with a direct line over the attic to the soffit area with a vent port out of the soffit. This duct is insulated and is only about 5 ft long (while the old system - duct was approx 12ft long) I purchased the vent port from a friend that does HVAC work. It made specifically for venting fans in soffits and actually "twirls" the air as it leaves the port (grill). This twirl effect causes the air to be directed out away from the house.
I think this system will work much better than the original -shorter pipe -no screen in the system to clog up -no vent on the roof (got covered in the winter with snow) -the vent port is close to a outside deck so I can keep an eye on it.
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Hi Iderooy,
Any idea who makes that "vent port"? Part number? I'd like to give that a try...
Thanks. -Mike
lderooy wrote:

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