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I've read many of the other questions about venting thru gable, but this seems slightly different. I discovered my upstairs bathroom fan is venting to the gable vent. Not ideal, I know, but may be ok enough in this situation. The wind and snow blows 99% of the time from opposite side of attic through this gable, so no moisture or precipitation is coming back in the attic there. It's rigid duct from fan to close to gable vent, then transitions to cheaper flexible duct for the final inches to gable screen. From the pic, you can see the rigid duct is angled down, then the flexible duct rises up several inches. It appears the flexible have separated a little from the rigid, so I'll have to go in and tape that.

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  1. Wouldn't vented steam cool and collect in that dip?

  2. Should I cut the flexible ducting back so it meets the screen in the bottom corner, not 1/3 of the way up?

  3. Should I raise the rigid with something so the angle points a few degrees upward instead of downward, allowing the hot air to rise up and out naturally?

  4. Or should I just cut a roof vent above the fan to vent it out there? The roof above attic is hit hard with wind and lots of snow, so the gable venting may be better in this situation.

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I would raise the rigid just so it's not going down into the insulation and then refit the flexible straight to the gable screen. There's a very little chance of any moisture accumulating anywhere in the duck run. If any did, it would evaporate quickly like the water does under your fridge. I would stay away from cutting a hole in your roof. The venting you have now should be totally sufficient. Putting a countdown timer on the vent, if separately switched, is always a good idea because you can run the vent for a longer period of time and don't have to remember to turn it off.

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    I agree, especially with the count down timer (required in my jurisdiction) I thought flex ducting run horizontally was a bad idea and thought it would pick up moisture but after checking it both at the fan and the exhaust I could not find any moisture. That was the first time I ever used it and had 2 90’s and a up and over a hvac duct all in 8’ some 20 years later never a drop of water from that exhaust where the shower was used daily.
    – Ed Beal
    Oct 20 '20 at 0:12
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I'd definitely make sure it didn't have an area to collect condensation.

What kind of venting does your roof have? Do you have a ridge vent, roof vents higher up and the gable is your intake air? Do you have soffit intake vents?

If the gable is serving as your input air for venting out the upper vents in the roof then I don't like the idea of have an air output pushing out an air intake vent.

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