Bathroom fan exhaust routing

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  #1  
Old 04-28-18, 09:47 PM
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Bathroom fan exhaust routing

Which is preferred for bathroom fast exhaust: vertical out the roof, or horizontal out the side? Right now, two upstairs bathroom fans vent into the attic, terminating right up under the ridge vent, which is not great. We're getting a new roof, and if vertical is preferred, now would be the time to do it - it'd be pretty easy to have them slightly rerouted and extended out through the roof. But if horizontal out the side is preferred, I'll leave them as they are and either try myself or have someone do it at a later time.

Going out through the roof would be simpler, but then I'd have two more roof penetrations...
 
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Old 04-28-18, 11:21 PM
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Personally, i prefer to run them horizontally along the ceiling joists, so that the duct can be covered with insulation... Then when they get near the roof, turn them up where they can hook up to a dampered roof louver. That way you don't have a lot of ininsulated vertical pipe.
 
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Old 05-27-18, 12:11 PM
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Sorry for the long pause there, got busy with other things...

So I think I'm going to go out the sidewall of the attic instead of putting two more holes in our roof. I'll either use straight 4" metal ducting or pvc for 100% leakproofness.

What I'm unsure of is how to go about getting a hole in the side of the house and then putting a cap on the outside (house has vinyl siding). Does anyone have a recommendation for a specific sidewall vent cap? I've seen a few caps, but they look like black metal. Are there vinyl ones which would match the siding color? And how do you attach to the siding - use a mounting block?
 
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Old 05-27-18, 12:24 PM
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You use a vinyl siding dryer vent mount. Use a 4 1/4" hole saw. Drill through the siding and sheathing to make your hole. Then remove the piece of siding and install the mount on your sheathing. Measure and use a tin snips to cut the hole in the siding square to fit the mount... Then put the siding back on. Then snap the trim ring on. You can drill from the inside out if it's easier to locate the right spot to drill.
 
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Old 05-27-18, 11:19 PM
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OK, great. Thanks. I see two basic types. I'm favoring the second one because I saw some mention of moisture possibly freezing the flaps on the first type shut in cold weather. (Sorry for the ridiculous largeness of these images...)
 
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Old 05-28-18, 04:36 AM
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Yes, as far as the installation goes, the only difference is that the 2nd one doesn't have a removable snap ring. You would need to position your hole so that it is on a horizontal seam, then remove 2 pieces of siding instead of one. The lower siding will slip into the flange from the bottom, then the top piece will slip down around the top. You will also need an unlock tool to zip the siding back up. (Malco sideswiper).
 
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Old 05-30-18, 03:11 PM
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XSleeper, you've been a big help. Thanks for providing your opinions.

But I keep going back and forth with this. As I said, the ducts already are there, going up to just under the ridge vent. It would be fairly easy to reroute them a bit so that they could exit the roof somewhere downslope from the ridge, and the roofers could do the cutting of the deck and installation of the boots and flashing while they are shingling. But then I'd have two more penetrations of the roof, and the continuing possibility of condensation leaking down into the bathrooms, and they could be buried by snow.

Changing so they run horizontally out the side of the house would be a short run; it's only 3-4 feet, and I wouldn't have to worry about condensation drippage or snow. The only thing is, that side of the house is above the sloped roof of the garage, and I'm not inclined to be setting up a ladder on a sloped roof to get up there to cut through the siding, etc.

Which would you go with if it was you?
 
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Old 05-30-18, 03:40 PM
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I have done it both ways. The problem with straight up is condensation running down. You eliminate that problem if you keep it low, and you run horizontal and pitch the pipe to the outside like a drain.

If you go through the roof you use a 4" damper roof louvers. Broan is a common brand. If I go up it's usually low on the roof, nowhere near a gable end.
 
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Old 05-30-18, 09:42 PM
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OK, yeah, I think accessing the gable end way up above the sloped garage roof is gonna be too much of an adventure. I guess I can go horizontal to a spot fairly low on the roof and then go up (I know that was your first suggestion way back...). Thanks for helping me work through this and finally make a decision!
 
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Old 05-31-18, 09:08 PM
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Glad to help. Thinking things through like that is always a good idea.
 
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Old 05-31-18, 10:23 PM
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One more question on this: when going through the roof, would you avoid cutting the hole right alongside one of the rafters, as in the #1 position in this photo, with something like the #2 position being better? (When actually doing it, I would come down even lower on the slope, I'm just asking hole position in relation to the rafters. Yes, I tend to overthink every little detail...)
 
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Old 06-01-18, 05:12 AM
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That part really doesn't matter. As long as you are far enough away from the rafter to hook up the duct. You will want to put 2 short neoprene washer screws in the front edge of your roof vent. Be sure you don't strip them by spinning them too tight. You will want a 4 1/4" hole saw
 
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Old 06-02-18, 08:56 PM
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Thanks yet again!

(This is apparently too short of a message to post. I'm told it needs to be at least 25 characters, so I'm adding this needlessly long explanation to make it longer. So I guess this now qualifies...)
 
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Old 09-12-18, 09:52 PM
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Bringing this back from the dead...the roofing project was delayed, but moving forward now.

For the vent on the roof, which type is preferred, the pipe style, or the low louvered vent style? I'm a bit worried about the louvered style getting covered by snow or the flap freezing shut. I don't think those would be problems with the pipe style, but it seems like almost every bathroom exhaust vent is the louvered type. Is it goofy to have a pipe style vent for bathroom exhaust?
 
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Old 09-13-18, 02:50 AM
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The pipe style is more problem free.
 
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Old 09-13-18, 05:09 AM
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installing it in the soffit will take all the roof issues out the mix.
 
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Old 09-13-18, 08:35 AM
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OK, roger that. Going with the pipe vents.
 
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Old 09-16-18, 09:56 PM
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OK, so my plan is to have these vents installed by the roofers when they are doing my new roof. They say they can do it - the cost will be $185 each (and they are talking the low profile louvered type, I haven't told that I'd like the pipe type yet). But either way, my initial reaction is shock at $185 each. That seems crazy to me. I mean, they're already gonna be up there putting on the roof - all they need to do is cut a whole in the decking where I tell them to and install them. Am I wrong thinking that's too much?
 
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