I m using the same product on my home in northern VA and havent had a problem. They just mildew easily. Warm moist air hits cold air. I do have the pipe in the attic insulated, but not sure that really does anything. If yours are freezing, take a look and see how much ice is on them when that happens. I would consider spraying with silicone as well.
We use these:
https://www.homedepot.com/p/Everbilt-Soffit-Exhaust-Vent-SEVHD/203626521
IRC has some restrictions on location of vent outlets near windows and doors. I have not researched it, but the AHJ for most of our projects interprets it as 36" horizontally from any window, operable or otherwise. They may be wrong, but it has not been a problem so we haven't fought it.
I have installed those many times. They should be tight to the outside of the soffit to ensure the warm moist air is not being drawn back up into the attic.
Those vents from the OP are not intended for soffits. They are wall terminations.
This is something that I am trying to do (add bathroom fans to an old house) so this thread is very relevant .
The big problem I have seen from a number of sources i have been researching is that venting to soffits is a problem if the soffit itself is vented to the inside of the roof. What it will do is try in the hot moist air into that area and cause mildew and mold to flourish. They almost always recommend venting through the roof shingles etc with a specialized fitting . I think there are videos on youtube from This Old House explaining this and showing how to do the install.
They're for soffits.
http://dundasjafine.com/product/soffit-dryer-vent-2/
The thing is that they're showing it installed on solid soffits.
I consider a closed soffit to essentially be a wall.
Technically, you're right but not the kind of soffits the OP has. I consider a closed soffit to essentially be a wall. With vented soffits, there is no point in having these things.
You need a vent . You can’t vent into and attic. That would be stupid to say the least and against code.
Whatever you do, when you reassemble the vent outlet put a piece of screen between the ducting and the vent outlet. Last summer I had wasps build a nest in the vent piping about 6" in. I took a shower one morning (fan on), then shut the fan off and sat down to take care of some pressing business. While sitting on the toilet I see a bunch of insect legs sticking out of the fan grates. Fortunately the fan grates were too small for the little bastards to get through. That nest had around 30 wasps on it. I ripped the whole works out and replaced it as the fan was builder grade. A piece of screen across the duct on the outside of the house should prevent any repeats.
Nobody is saying not to have a vent. You just install your ducting flush to the vented soffit and let the bathroom fan blow the hot, humid air out of the soffit. Depending on the time of day and the weather, this air will then be immediately drawn back up into the attic space due to the soffit and ridge vents doing their job. Kind of dumb but venting a bathroom fan to a vented soffit is stupid to start with and should not be done for this reason. You don't then go increasing your problems by installing doors that freeze shut. I am just trying to help the OP solve at least one issue. Ideally, he should vent those fans out the roof or gable or somewhere other than his vented soffits. I never suggested that he just let the bathroom fans vent into the attic.
Is the ductwork insulated? If not, I would start there.
The duct work is installed, cause they open when its not super cold.
