Bathroom fan question

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Tom_T
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Bathroom fan question

Post by Tom_T »

I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
Jboglecmu
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Re: Bathroom fan question

Post by Jboglecmu »

We just did the same during a remodel. Fans were vented to attic. Didn't cause any damage, but definitely not optimal. Our contractor had a roofer come vent them through the roof since the bathrooms are on the 2nd floor.
Jboglecmu
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Re: Bathroom fan question

Post by Jboglecmu »

We just did the same during a remodel. Fans were vented to attic. Didn't cause any damage, but definitely not optimal. Our contractor had a roofer come vent them through the roof since the bathrooms are on the 2nd floor.
wallygator
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Re: Bathroom fan question

Post by wallygator »

Just run the exhaust pipe to a soffit vent no need to go through the roof...
squirm
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Re: Bathroom fan question

Post by squirm »

Is there a shower in the bathroom? If not it's ok to only vent the smells into the attic.
unstartable
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Re: Bathroom fan question

Post by unstartable »

Bathroom fans should vent through the roof, gable, or wall. I would not vent one though a soffit.

Edit to add link: https://www.beantownhi.com/post/2019/03 ... -or-soffit
Topic Author
Tom_T
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Re: Bathroom fan question

Post by Tom_T »

Yes, there's a bathtub/shower. It gets moldy so I really want to start using a fan.
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Sandtrap
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Re: Bathroom fan question

Post by Sandtrap »

Tom_T wrote: Thu Apr 22, 2021 7:02 am I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
Suggestions:
1
Install the largest and quietest (will not be the cheapest) bathroom ceiling fan you can afford.
2
Run a solid duck to vent in an adjacent gable end wall of the roof (sideways) if that is available. Put in a flapper vent on the outside and trim it out.
(avoid additional roof penetrations = leak area)
3
Run a duck to an existing duck and tap into that.
4
Run a duck to a soffit vent if that is practical and you are unable to do the above.
5
Keep venting to the attic like the old vent if the above can't be done, and there is no other option that you can do.
6
Put in a timer switch in place of the bathroom vent wall switch. Multiple buttons that select from 15 minutes to 2 hours. Like that. This is so that the vent can continue to run after someone uses the bathroom and closes the door. Thus, venting humidity and "stinkies" (technical term).

A competent carpenter can do all this work.
Call a roofer if there is a roof penetration so it will be flashed properly.
No permit needed in most cases.
Do not call an incompetent handyman who might "jurry rig" things.

j :D
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cheese_breath
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Re: Bathroom fan question

Post by cheese_breath »

You probably can do it yourself. If not, any handyman can. Just run a flexible vent line from the fan to the attic wall. Cut a hole in the wall and install an exhaust dryer vent.
The surest way to know the future is when it becomes the past.
clutchied
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Re: Bathroom fan question

Post by clutchied »

Tom_T wrote: Thu Apr 22, 2021 7:02 am I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
when we had insulation added they suggested using an extension to vent it up next to the ridge vent instead of another puncture.

Let's the stack effect do the work.
pshonore
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Re: Bathroom fan question

Post by pshonore »

cheese_breath wrote: Thu Apr 22, 2021 8:33 am You probably can do it yourself. If not, any handyman can. Just run a flexible vent line from the fan to the attic wall. Cut a hole in the wall and install an exhaust dryer vent.
I would not recommend this approach. I did it one time. I live in CT so the winters are cold. The moisture (from showers) condensed to water in the flexible duct in my cold unheated attic and blocked it when the weight of the water deformed the flexible duct. Using a 4" dryer metal vent pipe with a slight pitch to the dryer vent in the wall is the way to go.
rich126
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Re: Bathroom fan question

Post by rich126 »

Sandtrap wrote: Thu Apr 22, 2021 8:31 am
Tom_T wrote: Thu Apr 22, 2021 7:02 am I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
Suggestions:
1
Install the largest and quietest (will not be the cheapest) bathroom ceiling fan you can afford.

j :D
While I can understand some wanting quiet but when it comes to bathrooms I prefer something not so quiet in order to "hide" other sounds coming from a bathroom :wink:
----------------------------- | If you think something is important and it doesn't involve the health of someone, think again. Life goes too fast, enjoy it and be nice.
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bestoftimes
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Re: Bathroom fan question

Post by bestoftimes »

Sandtrap wrote: Thu Apr 22, 2021 8:31 am
2
Run a solid duck to vent in an adjacent gable end wall of the roof (sideways) if that is available. Put in a flapper vent on the outside and trim it out.
(avoid additional roof penetrations = leak area)
3
Run a duck to an existing duck and tap into that.
4
Run a duck to a soffit vent if that is practical and you are unable to do the above.

j :D
I just want to point out that it is often difficult to get ducks to run... :wink:
Topic Author
Tom_T
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Re: Bathroom fan question

Post by Tom_T »

clutchied wrote: Thu Apr 22, 2021 8:34 am
Tom_T wrote: Thu Apr 22, 2021 7:02 am I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
when we had insulation added they suggested using an extension to vent it up next to the ridge vent instead of another puncture.

Let's the stack effect do the work.
The location of this bathroom is such that it is located almost directly under the center of the roof, middle of the house. Nowhere near a wall. The distance from the attic floor to the roof isn't far -- maybe six feet? You could stand, but you'd watch your head.
crefwatch
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Re: Bathroom fan question

Post by crefwatch »

Besides the Dryer duct 4" circular hood/flapper product, I have used a plastic cage specifically designed to be mounted on a horizontal overhanging soffit. (That is, a level, flat panel near the lowest course of shingles. It would be hidden by a gutter, if there is one. All parts are plastic, and it's not quite as rugged as the aluminum dryer product. But it does that specific job.

I have also run (myself) bath fans to 8" wide wall (vertical) aluminum vents. There is a minor problem in that these vents are (?) designed for kitchen exhausts, which have more oomph. So the closing spring (absent on dryer outlets) on the outdoor louver only opens about half-way, even with a 150 CFM bath fan. This may slightly reduce the fan's delivered CFM.

Note that many bath fans have a plastic (gravity) louver at their immediate output, which should be cleaned yearly or every two years, along with the fan blades.

I live in northern NJ. I think my 1955 ceilings leak enough heat that I haven't had a problem with freezing or condensation. In one job, I used very flexible plastic 6" duct that was a pre-insulated sandwich. So a 4" to 6" transition was needed near the fan.

Edit: Automatic humidistats with auto-shutoff timers are coming into use. Home Depot has add-on single-device wall-box humidistats. I prefer not to have a fallible device embedded in the fan itself. I do worry about whether the fan will come on, unsupervised, during a hot, humid August day in NJ, without the shower being used.
Last edited by crefwatch on Fri Apr 23, 2021 10:09 am, edited 1 time in total.
squirm
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Re: Bathroom fan question

Post by squirm »

rich126 wrote: Thu Apr 22, 2021 9:41 am
Sandtrap wrote: Thu Apr 22, 2021 8:31 am
Tom_T wrote: Thu Apr 22, 2021 7:02 am I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
Suggestions:
1
Install the largest and quietest (will not be the cheapest) bathroom ceiling fan you can afford.

j :D
While I can understand some wanting quiet but when it comes to bathrooms I prefer something not so quiet in order to "hide" other sounds coming from a bathroom :wink:
Yes! I want loud powerful fans!
clutchied
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Re: Bathroom fan question

Post by clutchied »

Tom_T wrote: Thu Apr 22, 2021 12:07 pm
clutchied wrote: Thu Apr 22, 2021 8:34 am
Tom_T wrote: Thu Apr 22, 2021 7:02 am I bought my house 20 years ago. It's relatively old, circa 1962. One of the bathrooms had been redone, and a fan was put in. Here's the thing: the fan vents into the attic. I guess this was standard practice way back when? As a result, I've never used the fan because I suspected that venting into the attic was a bad idea.

So, now I'd finally like to put in a new fan for proper use, reduce mold, etc. I need an installation that would vent the fan through the attic to the roof, correct? What type of contractor would I call to do this?
when we had insulation added they suggested using an extension to vent it up next to the ridge vent instead of another puncture.

Let's the stack effect do the work.
The location of this bathroom is such that it is located almost directly under the center of the roof, middle of the house. Nowhere near a wall. The distance from the attic floor to the roof isn't far -- maybe six feet? You could stand, but you'd watch your head.
I guess the question is do you have ridge vents which run along the cap of your roof line or something else?

For my install they literally just took a flexible hose capped the vent and then ran the line up just below the ridge vent so that as air exhausts out of the attic it pics this up and takes it with it.
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RickBoglehead
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Re: Bathroom fan question

Post by RickBoglehead »

A couple of comments:

I can't imagine this was ever code. Venting moisture into an attic is a no-no.

For those that think that venting into the attic below the ridge vent is ok:

- Make sure you have a positive air flow OUT the ridge vent. Sometimes the airflow isn't in the direction you think it is. :shock:

- When it's -10 out, go take a long, hot shower. Then open the attic stairwell and see if there are pretty icicles on the inside of the attic by the ridge vent, or hanging off the hose.

We sold a cottage last Fall that we inherited. Father in-law had not vented one of the fans out the roof, so that was remedied with a new roof years ago. However, the hose had disconnected by an inch, hanging on tape, and we didn't notice until the home inspection when the mildew was nice and obvious. Luckily, the home inspector said "fix that, spray the ceiling with bleach, and I won't put it in the report" and we did. The home had many issues, all of which (except that) were disclosed on the Seller's Disclosure, and this wasn't even notable given that.
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Reamus294
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Re: Bathroom fan question

Post by Reamus294 »

I used an in-line fan installed in the attic vs a fan that is installed in-ceiling. They are much more powerful and quiet. If I was asking a contractor to do it, I’d make sure there is a damper that closes when the fan isn’t in use, insulate the exhaust piping, and install a timer switch.
I went through the wall since it was easy to access in the attic, and the outside exhaust has a bug screen and another damper. If you go with an in-ceiling fan the panasonics are top notch.
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Bogle7
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Re: Bathroom fan question

Post by Bogle7 »

Panasonic WhisperGreen os the fan you want.
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lthenderson
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Re: Bathroom fan question

Post by lthenderson »

RickBoglehead wrote: Thu Apr 22, 2021 1:30 pm I can't imagine this was ever code. Venting moisture into an attic is a no-no.
There were no national codes on this until the early 2000's so any houses built before then were likely to vent in the attic unless a local code was more strictly written.
UALflyer
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Re: Bathroom fan question

Post by UALflyer »

RickBoglehead wrote: Thu Apr 22, 2021 1:30 pm A couple of comments:

I can't imagine this was ever code. Venting moisture into an attic is a no-no.
In a lot of warmer states, there's no problem with venting bathroom vents into the attic and it frequently is/was up to code. In those warmer states, you have warm and moist outside air circulating in the attic anyway, so adding a tiny bit of moist air doesn't make any difference. Winters are also not cold enough there to cause condensation issues that you end up with in places with colder winters.

One of the downsides of having it vent through your roof is the fact that roof penetrations have to be sealed and maintained. Over time, seals deteriorate and you can end up with roof leaks, which can cause far more problems than venting it into the attic could've ever caused (in warmer states).
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