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Old 08-08-2011, 12:37 PM   #1
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Bathroom Fan Venting


I'm fixing up a house for rental and have a question concerning bathroom vent fans. This house already has them. Two in all, one in each bathroom. They are older three inch diam. types. These fans are currently not vented outside of the attic. I want to correct this problem and I'd like to do it properly. My questions are the following:

  1. Can I tee them and vent them through one opening or do they need separate ducting and outside exhaust vents?
  2. They are located in adjacent bathrooms and the fans themselves are only about 5 or 6 feet apart. They are located next to and below a gable vent. Can I duct them to the gable vent and leave it at that?
  3. If I need to go through the gable wall, where can I buy the parts I need to complete the transition through the exterior wall which currently has white vinyl siding on it. (I'm guessing a vinyl supply house)

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Old 08-08-2011, 01:14 PM   #2
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Bathroom Fan Venting


The fan would have to be after the T so you don't push air from one bathromm to the other. You can get a remote bathroom fan (google it) and mount it in the attic space.

To go through the wall just get a wall vent and good quality sealant.

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Old 08-09-2011, 02:14 AM   #3
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Bathroom Fan Venting


Bath fans are what you need to eliminate moisture and odors
They should both be seperate from each other and should be minimum 100cfm fans.
In my house I would make sure they are both Energy Star rated.
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Old 08-09-2011, 08:04 AM   #4
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Bathroom Fan Venting


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Originally Posted by shazapple View Post
The fan would have to be after the T so you don't push air from one bathromm to the other. You can get a remote bathroom fan (google it) and mount it in the attic space.

To go through the wall just get a wall vent and good quality sealant.
I get the concept of the remote fan although I was unaware of their existence. It answers my concerns about "T"ing two fans together as I knew there would be a probable cross over problem. Since the existing fans are both in good working order I don't think I'll replace them. I guess, unless I find a back up prevent-er I'm resolved to vent each of them separately. As for the wall vents, the only one's I find at the Big Box stores are dryer vents. I guess they are basically the same thing just a bigger diam. It's been pretty hot here lately. This is one of those projects I'm dreading because of the attic time. I guess I'd better suck it up and git-er-done.
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Old 08-09-2011, 08:15 AM   #5
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Bathroom Fan Venting


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Originally Posted by REP View Post
Bath fans are what you need to eliminate moisture and odors
They should both be seperate from each other and should be minimum 100cfm fans.
In my house I would make sure they are both Energy Star rated.
Because of their age I doubt these are Energy Star. If I were buying new I'd do the same, but I don't find it green to junk perfectly good fans, and as you're probably aware the amp draw by these small fans are pretty minimal. As you mentioned the fans are used to remove humidity from the bathrooms which is why I was wondering about T-ing them. Sounds Like remote fan mentioned by Shazapple is the work around for mutiple locations. Looks like I'd better get up early to beat the heat and get a couple of exterior vents covers installed.
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Old 08-09-2011, 09:02 AM   #6
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Bathroom Fan Venting


I do not like Ting them,There is little advantage in doing so.That plus it would have to be a big fan in order to get 200 cfm if both are being run at the same time,plus you would be taking out the conditioned air from both rooms when you only need to take out air from one room.
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Old 08-09-2011, 11:22 AM   #7
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Good Point.
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Old 08-09-2011, 11:48 AM   #8
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Bathroom Fan Venting


You can buy backdraft dampers and put them on each line before the Tee, preventing air from moving back into the other room. BUt if both fans are run together, this will impede airflow (2 fans venting through one pipe). Newer fans (and maybe older ones too) have dampers built into them as well.

You can get a vent hood in a big box store or hvac supply store. Here is an example of one that is meant to put on siding:
http://www.flashlightz.com/product.p...&category=1095


Example of a 3" damper: http://stores.hvacexpress.com/-strse...per/Detail.bok
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Old 08-09-2011, 12:01 PM   #9
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I'd go with a remote inline fan as suggested, they are very powerful. I installed one in my basement and have it venting through a dryer style vent for my upstairs bathroom, the run is at least 25 feet of some spiral, ABS and metal pipe and it still works great after over a year. The reason I did it that way was my soffit was physically inaccessible due to the pitch of the roof.

It's not recommended to vent through the roof because once the fan stops you'll have hot moist air sitting in the pipe, which will eventually freeze, this will cause frost on that inside of the pipe (does not matter if it's insulated) and when you go to use the fan again this frost will melt and it could cause water issues. May not see it right away but eventually enough frost will build up. This is probably a bigger issue in climates that get -30's so in the south it's not really an issue.
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Old 08-09-2011, 12:57 PM   #10
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Quote:
Originally Posted by secutanudu View Post
You can buy backdraft dampers and put them on each line before the Tee, preventing air from moving back into the other room. BUt if both fans are run together, this will impede airflow (2 fans venting through one pipe). Newer fans (and maybe older ones too) have dampers built into them as well.

You can get a vent hood in a big box store or hvac supply store. Here is an example of one that is meant to put on siding:
http://www.flashlightz.com/product.p...&category=1095


Example of a 3" damper: http://stores.hvacexpress.com/-strse...per/Detail.bok
Quote:
Originally Posted by Red Squirrel View Post
I'd go with a remote inline fan as suggested, they are very powerful. I installed one in my basement and have it venting through a dryer style vent for my upstairs bathroom, the run is at least 25 feet of some spiral, ABS and metal pipe and it still works great after over a year. The reason I did it that way was my soffit was physically inaccessible due to the pitch of the roof.

It's not recommended to vent through the roof because once the fan stops you'll have hot moist air sitting in the pipe, which will eventually freeze, this will cause frost on that inside of the pipe (does not matter if it's insulated) and when you go to use the fan again this frost will melt and it could cause water issues. May not see it right away but eventually enough frost will build up. This is probably a bigger issue in climates that get -30's so in the south it's not really an issue.
Thanks for input guys. secutanudu, how'd you know I have white siding?
Thanks for the links, could not find a damper in the Big Box Stores.

Red Squirrel, Same problem for me. Roof has a 5/12 pitch so no way to get to an eave. Luckily the bathrooms are next to each other on the gable end of the house. I think I'll just stick to my resolve to vent them separately through the gable wall. The roof is just more work, but frost here not that big a problem.

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Old 08-21-2011, 05:09 PM   #11
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Bathroom Fan Venting


Got the work done on the bathroom fan vents. Finished them up last week, but forgot to post a follow up. They came out great.

From inside the attic I used the lowest louver on the gable vent as a point of reference and measured from the center of the bottom louver to the a gable stud cavity closest to each vent. I also accounted for possible obstruction and noted that I should drop down a few inches below the vent to clear framing braces.

Then I went out side and measured off the center of the bottom gable vent louver, dropped down a few inches and made sure I was cutting through on sheet of vinyl siding. I made a small pilot hole in the center of where each vent was to go. Then using the pilot holes as a guide I cut the holes with a 4" hole saw connected to my drill.

I slide the duct boot attached to the vent cover into the holes and screwed the covers to the siding. I also caulked the top and sides with a white silicone to avoid weather leaks.

I used a 3" to 4" enlarger attached to each fan. I connected each vent boot to the closest fan with a section of expandable and flexible aluminum ducting. Pipe clamps and foil tape.

I have trusses in my attic and all of the work had to be done squatting. I did use a couple of 1"x12"x30" planks to to squat on so i didn't have to perch on the 2x4 trusses. It was pretty hot in that attic and I'm glad it went relatively easy. Thanks again for the advice and encouragement.
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Old 08-25-2011, 12:46 PM   #12
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Bathroom Fan Venting


Pete,

I am doing the exact same thing in my home. Two bathrooms right next to each other.

I am planning to use one of these:
http://residential.fantech.net/resid...-exhaust-fans/
and connect both bathrooms to one fan. I am also thinking of somehow controlling the dampers on the inside vent to the timers I will install on the walls to operate the fan.

Can you post pictures of the attic space and how you ran the ducts with dimensions.

Thanks
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Old 08-25-2011, 01:52 PM   #13
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Quote:
Can you post pictures of the attic space and how you ran the ducts with dimensions.
Man, you're asking a lot when you ask a guy to climb through his attic in this heat.

Actually, I'm heading over to the house this afternoon. We live in Virginia Beach so we're getting ready for the "Irene" factor Late Friday or Saturday. The wife and I just made a 5 hour round trip to our Northern Virginia campground this morning to close up our Pop Up campers and make sure everything else is secure.

I'll take the camera with me and if time allows I'll get up there and take some pictures. Not that much to see really and these are individual fans that were there already. They'd just never been vented outside the attic.

Having glanced over the installation manual for the link you posted, I doubt what I have done will be of much use to you. Also, it looks like you will need to wire that device with 3-way switches to use it for two bathrooms.

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Old 08-26-2011, 05:33 PM   #14
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Bathroom Fan Venting


I did not get a chance to post this yesterday. Hurricane coming. All the hatches are battened down. Here is a link to the pictures. They were all taken after the fact. I hope this helps.
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Old 08-26-2011, 05:53 PM   #15
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This is awesome Pete, thanks.

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