# Bathroom Exhaust Vent



## algored2deth (Jan 7, 2011)

Welcome to the forum!!!

The vent should exit at the roof. Use rigid pipe with insulation (a fiberglass wrap most likely) and seal up all seams at the two end connections with caulk. Also seal the exhaust fan box to the ceiling drywall with spray foam or caulk (use best judgment here). Venting at the soffit provides a chance for moist air to recirculate back into the house. Use a good quality vent that is sturdy. Moisture can come back if your vent pipe is not insulated because you will have warm bathroom air meeting with cold attic air.


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## jklingel (Dec 21, 2008)

You can also spray foam the pipe till it gets outside. I put 2-90 elbows (ie, 180) on my 3" ABS vent pipes just for the water issue.


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## Just Bill (Dec 21, 2008)

Rain or snow should not be an issue. Roof caps have a flapper that only opens one way, and wind will actually hold it closed tighter. Condensation inside the vent pipe is sometimes a problem. As suggested above, insulating the pipe up to the roof exit will reduce this problem.


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## Daviddasdj (Mar 24, 2011)

Thanks for your replies. The vent that I installed does open with the wind...I heard it the other night flapping away, when we had strong winds and snowfall the next morning a found a small wet patch on my bathroom rug... so are there different kinds of vents or better quality vents?


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## algored2deth (Jan 7, 2011)

Yes, you can go to HD, Lowes, etc and check out different versions. Braun makes them (as an example). They should have a flap that shuts when the indoor fan is not running. Build quality varies in terms of the sheet metal that the vent is made from. Also check with bldg supply stores as they may have something made with a heavier gauge of metal. Plumbing supply stores might have something...


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## Mike Mike (Feb 9, 2011)

I've just gone through the roof vs. soffit battle at my place, so wanted to add my 2 cents for anyone researching this issue. It may save you my pain.

I tried it through the roof. I live in Ontario where it can get very cold. I used flexible pipe up through the roof with one of those small Broan vents with the flapper. I insulated it to prevent condensation. It did not work. We got condensation dripping back through the fan.

The only downside that i see to venting through the soffit is the potential for moist air to re-enter the attic. However, venting through the roof has many disadvantages. Extra hole in roof means potential for leak. Condensation can only drip downwards and back into fan. Insulation can be difficult to apply. Noise of the flapper. Snow buildup on the roof can plug the vent.

I have now changed it entirely. I am using rigid pipe out through the soffit. I angle the pipe towards the soffit so that any condensation that may develop will drip outside and not back in through the fan. I insulate it all around and cover it with some of the attic insulation also.

Will have to wait for winter to see if this is works better, but I suspect it will.

Also, if you do decide to vent through the roof, don't buy the crappy vent with flapper from Broan that they sell at Home Depot. There are other kinds that extend up higher to get above the snow and have a wind guard to prevent the flapping. A roofing specialty store should have one.


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## Mike Mike (Feb 9, 2011)

Further to the bathroom exhaust saga ....

As I mentioned, I now vent the exhaust through the soffit. I think I'm still getting some frost inside the vent pipe, but this is kind of inevitable. The section where it passes through the soffit is impossible to insulate.

Overall, I'd say it is working pretty well. My only additional advice is to use smooth-walled aluminum instead of galvanized. The galvanized will probably rust eventually.


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## mrgins (Jan 19, 2009)

Soffit for me. Easier to pitch the pipe and insulate


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## jklingel (Dec 21, 2008)

I built in '80 in Frb, and ran ABS pipe out through the roof. As mentioned above, I installed a 180 degree elbow at the end, and have never had water dripping back into either bath vent. A winged ghost appears around the pipe after long cold spells, but it has never closed in. (It may have once back in the early '80's, when we had some real nasty temps. ???) The DWV pipe does close once a year or so, as there is no fast, warm air to melt and blow and ice/condensation away (I gather). Run a fan with adequate CFM, and avoid long, steamy showers (saves on fuel, too). Be very careful venting through the soffit, as the likelihood of moisture getting back into the roof area is there.


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## Minus08 (Oct 31, 2011)

Daviddasdj said:


> Thanks for your replies. The vent that I installed does open with the wind...I heard it the other night flapping away, when we had strong winds


It flaps because of the low pressure area created on the outside of the damper by the high winds. The same way a plane's wing creates lift.

In my home I have 2 bathrooms upstairs and each exhaust fan was vented out the soffits. I questioned our home inspector about that and he said, The termination point for your fans is typical for the age of the dwelling. Since 2003 the building code changed to require that bath fans terminate directly to the exterior with a hood and back draft damper similar to that like a dryer vent. 

As soon as we took possession, that was the first thing I changed. Installed 2 roof vents and vented them out that way.

I believe This Old House had a demonstration once where the fan was vented out the soffit, and showed how the warm moist exhaust air would go right back into the continuous soffit vent.

If you decide to do soffit venting, just monitor the area for any signs of moisture collecting on underside of roof sheating


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## gcan (Dec 23, 2011)

Does anybody have a picture of the soffit venting?

My house is 1-1/2 story and the 3 bathrooms are spread through the house and I really don't want to put 3 holes in the roof. I haven't seen a soffit vent that I felt would perform very well.

Thanks in advance


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## mae-ling (Dec 9, 2011)

MY HVAC guy says To put the bath fan on the top of an inside wall. then duct it down the wall and out the floor joists. Insulate where it goes out the flor joists.


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## 4just1don (Jun 13, 2008)

mae-ling., so your mounting it on the vertical wall towards the top of exterior wall?? why exit so low then? seems it would reduce exterior wall insulation

If your using ceiling mount how do you get vent down thru top double plate to get to stud cavity and seems same question on why down to floor joists?


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## Minus08 (Oct 31, 2011)

gcan said:


> Does anybody have a picture of the soffit venting?


Two types of soffit venting. Continuous soffit and "indiviual soffit". First 2 photos are individual soffit vents and the last ywo are continuous type


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## mae-ling (Dec 9, 2011)

4just1don said:


> mae-ling., so your mounting it on the vertical wall towards the top of exterior wall?? why exit so low then? seems it would reduce exterior wall insulation
> 
> If your using ceiling mount how do you get vent down thru top double plate to get to stud cavity and seems same question on why down to floor joists?


Sorry if I was not clear. Mount in on an interior wall at the top of the wall. then down the interior wall turn it and out between the floor joists. Insulate well around it where it goes between the floor joists and out the wall.

If you are running it perpendicular to floor joists you would have to run it out a basement wall.

This is so cold air can not come down it and in or wind, as in a roof or straight out a wall installation.


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## gcan (Dec 23, 2011)

my house has the soffit vent but how do you connect it? or do you just run the vent to it? no connection?


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## bareshiyth (Jan 6, 2012)

Minus08 said:


> It flaps because of the low pressure area created on the outside of the damper by the high winds. The same way a plane's wing creates lift.


Exacty! Winds coming across the roof peak, especially, create a low pressure area.. Exactly why you must run chimneys up high enough to get outside the venturi/aerodynamic zone.

Another good approach, if you have a peaked roof and attic with gable, is put in a vent (dryer type) in that wall up near/at the peak and under the eave. Multiple vents? Run them together into a single aluminum vent pipe and out through that one exit point. (Even saves the heat - less moisture - for your attic!)


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## Minus08 (Oct 31, 2011)

gcan said:


> my house has the soffit vent but how do you connect it? or do you just run the vent to it? no connection?


You probably should terminate the duct into a vent like below. The easy way is to just terminate the duct into the soffit cavity. Probably not the right way. better to use a vent.

http://www.google.com/products/cata...=X&ei=vJMXT7yYKJPogQew0p2wAw&ved=0CI0BEPMCMAY


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## Minus08 (Oct 31, 2011)

Heres another termination vent from Home Depot:

http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053


and another from Lowes:

http://www.lowes.com/pd_317949-8533...rrentURL=/pl__0__s?Ntt=soffit+vent&facetInfo=


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## gcan (Dec 23, 2011)

wow - thanks - I didn't know they made soffit vents

So it sounds like I would 90 up from the fan, lay it on the ceiling joist and then 90 back down to these vents, with metal pipe? I assume I should also insulate the pipe? Or could I use like a flex duct that has insulation?


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## Mike Mike (Feb 9, 2011)

For those who make the point that soffit-vented moisture can travel back up into the attic ....

This is true, so for that reason, I blocked up the soffit 3 feet either side of the vent. I figured this should help quite a bit.


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## Minus08 (Oct 31, 2011)

Mike Mike said:


> For those who make the point that soffit-vented moisture can travel back up into the attic ....
> 
> This is true, so for that reason, I blocked up the soffit 3 feet either side of the vent. I figured this should help quite a bit.


 
Good idea. 

Probably not going to affect overall attic ventilation by losing 6 sq.feet of soffit venting. 

Beats the alternative of having that moisture come back up in attic, condense on framing members and start a mold issue.


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