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Old 05-30-2011, 06:45 PM
Join Date: Oct 2008
Location: Stars Hollow
Posts: 3,358
Bathroom fan venting into attic -- is this okay?

I actually have a bunch of attic questions.

Background: I have an attic about 35 or 40 feet long and about 4 feet high. One end of the attic has a set of louvers (sized about 3 feet by 3 feet) that are currently open. The other end of the attic has what I can only describe as faux-louvers. It's a rectangular window that looks like louvers but is in fact all plastic and with no ventilation at all.

First off, I have two bathrooms with bathroom fans. Each fan vents into its own white plastic tube which runs the length of the attic and ends up near the open louvers. However, the end is just hanging there, inside the attic, but next to the louvers. Is this okay, or will it cause a build-up of moisture and what not? Furthermore, is this up to code?

Secondly, I assume it's important to have the louvers always open. So, why is there only one set of functional louvers? It seems like they'd work a lot better at keeping the attic cool in the summer and cold in the winter with openings on both ends of the attic.

Thirdly, how can I keep birds from building their nests in the open louvers? There is wire meshing up against the louvers to keep birds and squirrels out of the attic, but it allows the birds to nest with impunity on the actual louvers themselves.
Old 05-30-2011, 06:51 PM
Join Date: Oct 2008
Location: Stars Hollow
Posts: 3,358
Missed the edit window:

Actually, fourth question: the louvers are currently open because I went up to the attic and removed the spring holding them closed. Why are they designed to stay closed constantly? There didn't appear to be any mechanism to allow them to remain open with constantly tugging on the handle, hence my removal of the spring. Is this an unusual design for louvers or are they broken in some way?

Thanks for all replies! I am no good at this home improvement/maintenance stuff. I wish I lived in a condo.
Old 05-30-2011, 07:05 PM
Robot Mod in Beta Testing
Join Date: Mar 2001
Location: Pennsylvania
Posts: 20,054
Generally speaking you don't want to vent your bathroom fans into the attic. The moisture build-up can cause mold problems and can also cause the wood holding your roof up to rot, and then when your roof starts to collapse you've got a really major problem on your hands instead of a minor one.

That said, I think the real issue here is how close is "close" when you say the vent is close to the louvers? If it is close enough that all of the moisture ends up basically venting out through the louvers anyway then it's probably good enough as-is.

Another issue is what is the climate like where you live? If you someplace where the air is regularly hot and humid anyway then venting a little hot and humid air into space that already has hot and humid air isn't worth worrying about.

ETA: A fake owl on the roof nearby may keep other birds away. It worked on my mother's house.

Last edited by engineer_comp_geek; 05-30-2011 at 07:06 PM.
Old 05-30-2011, 07:06 PM
Join Date: Jul 2009
Posts: 12,056
the plastic tube/duct should go to a vent through the wall, otherwise it leaves moisture in your attic especially when the attic is cold.

attics are best constantly and well ventilated, this helps both summer and winter.

place some chicken wire on the outside of the louver.
Old 05-30-2011, 07:20 PM
Join Date: Apr 2000
Location: Wash DC
Posts: 160
Was the spring holding the louvers closed attached to anything that would indicate there was supposed to be an exhaust fan in front of the louvers? There's no reason for holding the louvers closed unless there's a way for opening them for venting.
Old 05-30-2011, 07:24 PM
Join Date: Oct 2008
Location: Stars Hollow
Posts: 3,358
The exhaust tubes are hung right next to the louvers, but perpendicular to them, so the air probably stays in the attic instead of going out. I live in New England, so it's plenty humid, but I don't want to leave the status quo if it's not up to code. I want to sell this house, and I don't want the home inspection to turn up possible mold problems.

So, how ARE you supposed to hook up the exhaust tubes? I assume everyone has a bathroom fan, but I haven't noticed any dryer type exhaust ports on any of my neighbors' houses. Do I have to buy something and install it? I can't wedge the hoses in the louvers because of the aforementioned wire mesh.
Old 05-30-2011, 07:33 PM
Join Date: Oct 2008
Location: Stars Hollow
Posts: 3,358
Originally Posted by keno View Post
Was the spring holding the louvers closed attached to anything that would indicate there was supposed to be an exhaust fan in front of the louvers? There's no reason for holding the louvers closed unless there's a way for opening them for venting.
No, I don't see any evidence of an exhaust fan. I think I saw a label on the louvers when I was up there. I'll see what it says when I go up there again. It was a real bitch just to open the louvers temporarily which is why I had to remove the spring. (I'm gearing up for a return trip; it was at least 120 degrees up there.) That being said, I do have an attic fan at the other side of the attic, but the louvers do not open when the attic fan is turned on.
Old 05-30-2011, 07:35 PM
Charter Member
Join Date: Jun 2003
Location: Portlandia
Posts: 38,606
Exhaust vents are usually in the roof. They're easily installed by a roofer, and he can connect your bath exhaust to them (or might make you hire a plumber for that part). If your ducting is now running the entire length of the attic, it's probably too far to be effective. If you're having a roofer come over to install the vents, have him put in new flexible ducting to them by the shortest route possible.
Old 05-30-2011, 07:43 PM
Join Date: Apr 2009
Posts: 4,700
Bath designer here. To re-iterate, bath vents should NOT vent into the attic for the reasons mentioned above.
Old 05-30-2011, 07:47 PM
Join Date: Jul 2009
Posts: 12,056
short runs vertically are best or the shortest horizontally. a long horizontal run can have low spots that will have water condense and collect.
Old 05-30-2011, 07:55 PM
Join Date: Apr 2008
Posts: 3,833
As far as "up to code" goes... my house is a new construction (I've only been here a couple of weeks) and it had the same thing but they put in roof vents and fixed them before closing. I've read long threads on forums for home inspectors and, frankly, they don't even seem to know.

Vented to the outside is always best, however, many building codes consider the attic to be "outside" if it is well ventilated and some inspectors in the forums I read said they rarely see them vented to the roof on new houses anymore. Looking at the houses in my neighborhood, a lot of them have no visible vents.

I think mine would have been ok because the house has continuous soffit vents and can get breezy in the attic, but if in doubt, you can't go wrong venting to the roof.
Old 05-30-2011, 09:36 PM
Join Date: Aug 2010
Posts: 275
If you are venting your bathroom fan to the attic in a cold climate (think winter) you are asking for trouble. Maybe not now but in ten to twenty years it will cause trouble.

Most builders in north Idaho vent to the soffit with rigid pipe.
Old 05-30-2011, 10:23 PM
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 13,628
Venting vertically (through the roof) is best.
Venting horizontally (through a side wall) is OK, better than just into the attic.
Venting into the attic is bad.

Solid (metal or PVC) vent pipe is best.
Flexible metal vent pipe is OK (but real metal, not tinfoil coated plastic).
Flexible plastic is bad.

Louvers should be open generally. On both ends, so you can get ventilation (a breeze) moving through the attic. But they aren't as necessary if there is a good amount of overhead venting through the roof. (But if it's 120F in there in May in New England, you don't have enough.)
Old 05-31-2011, 10:30 AM
Join Date: Jan 2001
Location: Austin, Texas
Posts: 1,924
This may be a regional thing. I'm in Austin, TX where it's often hot even in February. I needed to get some of my rental properties to meet Section 8 (subsidized housing) standards, and one thing I had to do is add vent fans to each bathroom. The cheapest and easiest to install were those that vented directly into the WALL! Even in an uninsulated wall you've go a pretty small space to disburse the air. I even called the Section 8 people and told them I didn't think that was a very good idea, but they assured me that it passed the local codes and was OK.

I ended up installing them in the ceiling where they vent directly into the attic. Reading this thread has got me worried about even that. Of course this is Texas and I can't remember ever being cold in the attic.
Old 05-31-2011, 11:43 AM
Join Date: Dec 2005
Posts: 660
I bought a newly built house about five years ago. The bathrooms' fans vents into the attic. There is a flexible plastic duct sticking up about 3' from the insulation.
Old 05-31-2011, 11:43 AM
Join Date: Oct 2008
Location: Stars Hollow
Posts: 3,358
Thanks everyone for all the replies. Unfortunately, I probably don't have the money to do this right, but I will ask some roofers how much it would cost to do this. I think I remember some vents already in place on the roof, but I don't think they're currently being used. I don't have a tall enough ladder to get on the roof to check.
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