How to Insulate Bathroom Exhaust in Attic

Submitted by mcdiego t3_zxcu8y in DIY

I live in an older home where the bathroom exhaust fan blows directly into the attic via a semi-rigid hose that rises a couple of feet above the blown-in insulation.

With the recent cold weather, we're starting to get condensation that is dripping in the fan and into the bathroom.

Obviously, the ideal solution would be to properly vent to the outside, but that isn't a quick fix/feasible option at the moment. So I'm wondering if I could, for now, simply insulate the exhaust hoses.

Would wrapping them in something like this be effective? And stop the dripping?

Any other advice/tips would be great appreciated.

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RV_Web t1_j1zl7x0 wrote

With the recent cold weather, we're starting to get condensation that is dripping in the fan and into the bathroom.

Yeah, thats where you'll see the problem first. My guess is that its raining in your attic when the tropical rain fog comes billowing into the cold attic from your hot shower vent.

Would wrapping them in something like this be effective? And stop the dripping?

I would imagine if you shove enough of this around the pipe, it will soak up the water like a sponge and turn into a wet dripping stinking mess. So, yeah. sort of.

Obviously, the ideal solution would be to properly vent to the outside...

...Obviously...

but that isn't a quick fix/feasible option at the moment.

You do realize that one piece of flexible pipe run into a vented soffit, roof vent, or literally any other opening is better that just venting into the attic, right? And its not more expensive than the insulation wrap u show here, just slightly different to install.

My best advice is this..

Do you own it? Fix it right. Do you rent it? If so then leve it well alone and call the landlord and let him fix it or not.

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mcdiego OP t1_j1zxu17 wrote

>You do realize that...

Whatever phrase was to follow, the answer was no. I'm brand new to this :)

>it will soak up the water like a sponge and turn into a wet dripping stinking mess

This is essentially what I thought would happen, but some quick searches made it sound like that's all that was required. But that didn't make sense, which you pretty much just confirmed.

>Fix it right.

Yep, I know. Was just looking for a temp fix at the moment. I appreciate your help.

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unimatrix_0 t1_j228d7z wrote

If you have any open vents in the attic space, get some flexible pipe and temporarily have the air move right to the vent opening. You'll at least get much of it leaving. Then insulate the rest, and do it all properly in the spring.

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systemdelete t1_j1zkuhv wrote

If you insulate the pipe, you won’t condense in the pipe, you’ll move where it condenses to the first cold spot it hits in the attic. I’d vent it outside the roofline.

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mcdiego OP t1_j1zxy40 wrote

Yeah, the quick searches I did made it sound a little easy, but doesn't make sense on further thought. Thanks for the comment!

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ntyperteasy t1_j22019l wrote

Do get it fixed, as that moisture builds up and grows mold, and attracts small insects, which attract other insects, which attract mice, etc. The water is the first step in a thriving attic ecosystem....

As far as temporary fixes, you could extend the flexible hose to an eaves vent or to a gable vent and somehow secure the end of the flex pipe up against that vent for now. Then have a proper vent installed when you can, but don't wait too long...

I used a 4-inch "starting collar" (search your favorite hardware store for that part) to hold a piece of flex duct up against a gable vent until I could get a roofer out to install proper vents. It did the job... Bend the tabs to the side and screw it into place, then tape, zip-tie your flex duct to the starting collar. I wouldn't leave it like that for years, but will definitely get you through the rest of the winter.

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mcdiego OP t1_j22bgb4 wrote

Yes, definitely want to get it fixed before we have some new house guests!

After the roofer installed the vent, did you just use the same duct work from your temporary fix? And did you have the vent installed on the gable?

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ntyperteasy t1_j22deed wrote

I used pre-insulated flex ducting, which is good for this sort of vent (not good for a kitchen vent...) and just moved those over once the proper vents were installed. I decided to go straight up through the roof to keep the vent runs really short to minimize the chance for condensation. The gable would have been ok, but the nearest gable faced the street, so it would have been a bit ugly. If it was facing the side of the house, that would have been easier/cheaper and I would have done that. The original builder had left all three bathroom vents open into the attic ( grumble !%$?!) so I had them all fixed at once. It was a bit of a challenge to find a roofer to even show up for such a little job. In the end, I overpaid a guy $500 to install three vents into the roof (asphalt shingle). I had to go into the attic and attach my flex ducting to the inside of the new vents.

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redditor12876 t1_j22g1uc wrote

Don’t take a shortcut on that one you will regret it. Moisture in the attic means mold and rot. Both are very expensive to fix. A lot more than venting outside.

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aZamaryk t1_j1zkyap wrote

Can you run it to a soffit and at least get majority of the air out? Soffits should be open to outside for venting. You could possibly bury it in the blown insulation and just expose the end to soffit vent. Its not ideal, but it might help.

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mcdiego OP t1_j1zy5si wrote

I think I could run it to a soffit. Would it also work to run it to one of the mesh screens on the attic wall? They might be easier to get to than where a soffit vent is currently.

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aZamaryk t1_j200dcm wrote

Anyway to get it to exhaust to outside should help. If you have an eaves vent then go for that because that's hot air out and would help push bath air out. A soffit draws air in and might pull humidity back in.

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mcdiego OP t1_j202dw9 wrote

Okay nice. I’m going try for one of the eaves vents.

Any thoughts on how I should secure the hose to the eaves vent? Or could I get away with just resting it on there? Mainly thinking about a strong wind gust or something could move it off.

Really appreciate your help.

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aZamaryk t1_j2075du wrote

Buy one of those plastic discharge adapters and just screw it against the vent. You should have 2x4s around the eaves vent and should be able to just fasten it on an edge. Clamp or zip tie hose in place. Or if money is that tight you can always just screw the hose itself to the wood. Use washer to give more holding strength. A washer can be any flat item, piece of wood even.

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a_lost_shadow t1_j215wi1 wrote

If you vent out the soffit, consider using rigid ducting instead of a flexible hose. It's harder for a fan to push air through a flexible duct, so the fan will work better. It also allows you to put a small drop from the bathroom fan to the soffit exhaust vent. Doing so will allow any condensation that forms to drip out the soffit exhaust vent.

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saml01 t1_j205m1u wrote

They sell insulated exhaust vent tubing.

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Reelair t1_j205q2x wrote

Best bet is to vent it out of the soffit. You'll want to bury the vent hose in plenty of insulation, like 24" of insulation.

My mom has hers vented out a soffit, but it wasn't properly insulated. During the winter you could see a line in the snow on roof where the vent was run. This melted snow caused ice damming, leading to more problems. The duct was insulated, it was under about 12" of blown cellulose insulation, still wasn't enough. I put 2 layers of R20 on top of the vent, no more issues.

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JonJackjon t1_j20skn3 wrote

As a temporary "fix" can you extend the duct to a peak vent (if you have one).

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Pafkay t1_j21a5os wrote

It needs to be vented into the outside air, a vent in the attic is all kinds of wrong, you can then add a non return flap to prevent air blowing back down the tube

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creemurica t1_j24z1g3 wrote

Mine is vented out the side of the house with an insulated flexible pipe and it still drips in the bathroom sometimes when it’s cool outside and I take a hot shower.

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dUB_W t1_j1zl29s wrote

If the vent tube is pointing directly up, why not just put give it an s shape or a couple bends to trap the condensation higher up?

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hairysnowmonkey t1_j20ls41 wrote

That would make a goose neck flask like in chemistry class. Or basically a P trap where you don't want one.

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dUB_W t1_j20oj5o wrote

So do nothing then and live with the drip, got it.

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hairysnowmonkey t1_j20visf wrote

No I didn't suggest inaction. I suggested not intentionally clogging a dedicated vent tube with a pool of water as per that incredibly bad idea.

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dUB_W t1_j214bqc wrote

Dude said he didn't want to run a vent pipe out his roof. Insulation will not solve the problem of attic condensation dripping down his pipe. I suggest a solution, I've heard no alternative solution. Maybe a flapper at the top? That would have been a productive comment.

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hairysnowmonkey t1_j21gpw8 wrote

Many people offered superior solutions; mine would be redundant. A comment that precludes a detrimental unproductive "solution" is indeed productive. Did you try reading the other comments offering alternative solutions? Regarding correct venting? Have a good one.

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