bathroom vent fan

[woodbutcher]

When I built my house 15 years ago, I did not install a vent fan in the master bath. Now I'm finding that I need one. It will be fairly easy to vent it through the roof(after moving all my wife's stored items in the attic out of the way). Is there anything wrong with using thin-wall 4" PVC as ductpipe? I bought aluminum duct, but I can't find a Y-connector locally, and I'd like to connect the output from two vent fans so I'll only have one roof penetration. PVC seems like a good substitute.
It will be well insulated.
Butch

 

[bo]

Sure, why not? Heck, use schedule 40..it'll last longer. Or, use that corrugated dryer aluminum pipe...all the same.

 

[IH2444]

Put insulating sleeve on it to prevent condensation running back down in the fan.

 

[MO Jason]

My bathroom exhaust fans are ducted with the plastic/wire accordian type dryer vent duct and end in the attic- there's no reason you'd need to penetrate your roof for an exhaust fan- your attic should be vented enough. The sewer vent is the only thing that needs to be vented above the roof line for proper draft.

 

[kevinj54]

(quoted from post at 10:42:55 01/08/10) there's no reason you'd need to penetrate your roof for an exhaust fan- your attic should be vented enough.

Ever hear of MOLD???????????????

 

[Mike Groom]

They make a soffet vent for bathroom fans,you can hard plumb it or use flex vinyl pipe,if you don't let it exit out of the attic it might cause condensation in the attic.

 

[MO Jason]

Been that way for 9 years and no mold. The only time mold would be an issue is if you were venting a lot of hot humid air into the attic (during a shower) and that isn't really that much even then.

 

[kevinj54]

(quoted from post at 10:57:39 01/08/10) Been that way for 9 years and no mold. The only time mold would be an issue is if you were venting a lot of hot humid air into the attic (during a shower) and that isn't really that much even then.

If MO stands for Missiorri then I can see your point to some degree, but here in MI putting it in the attic in the winter will condense.

Our codes require all exhaust vented outside as I recall.

 

[Bspauld]

He said he could go through the roof,not vent it into the attic,thats the way I read it anyway

 

[MPK]

In Mn we use insulated flex pipe to prevent condensation from running back down.

 

[Stan in Oly, WA]

Hi Butch,

I'd do it exactly the way you've described: exhaust outside the attic, insulate the duct.

All the best, Stan

 

[woodbutcher]

Thanks for all replies. I do plan to vent through the roof because I am trying to take the moist air from the bathroom.
Butch

 

[schmuck]

The last house I owned had a master bathroom and bedroom added on to a hip style roof house. Someone had used the drier vent hose and vented that into the attic also. When it came time to re-roof, the sheeting over the add-on had to be replaced because it was moldy and the plies were de-laminating. Do what you want, but I'll never leave or install a vent in that fashion. By the way, if you aren't going to use the vent fan while taking a hot shower, why did you bother to put it in at all?

 

[Jon Hagen]

Two fans connected to a single outlet. If one fan on and the other off, might air from the running fan backflow into the room with the non running fan ? Most bathroom fans have a little flapper backflow valve that should prevent reverse flow.
Some fans do not have the backflow valve, and I removed the one in our bathroom. Removing that little flap valve allows natural draft to the outside vent which keeps the room dryer, fresher.

 

[Larry from MD]

The ones i have are vented outside under the eve of the roof. No extra hole to leak in the roof.

 

[D.B. in Mi.]

They used insulated flex pipe when they built our home.

 

[PJH]

I've seen "central" vent fans advertized in Fine Homebuilding magazine. I know absolutely nothing about them, price included, but the idea sounded interesting. A central fan with one outlet, mounted in the attic, and suction lines running to each bathroom. Probably would be quieter too.

Shame you can't go out the sidewall on a gable end and avoid yet another hole in the roof.

Should those vent tubes be sloped to drain condensation outside? I insulated and sloped my dryer and bathroom vents, but it might have been overkill.

Paul

 

[Dusty MI]

How about one of these? The fan is remount mounted.
Their from Grainger.

Exhaust Fan Kit,4 In
Item # 6C509
Exhaust Fan Kit, Remote-mounted, Fits Duct Dia 4 In, CFM @ 0.000-In SP 122, CFM @ 0.200-In SP 100, Max Inlet Temp 140 Deg F, Voltage 115, 60 Hz

FANTECH
PB100
3730 Usually ships
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$217.25
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Exhaust Fan Kit,6 In,115 V,214 CFM
Item # 3TJ96
Exhaust Fan Kit, Remote-mounted, Fits Duct Dia 6 In, CFM @ 0.000-In SP 214, CFM @ 0.200-In SP 190, Max Inlet Temp 140 Deg F, Voltage 115, 60 Hz

FANTECH
PB190
3730 Usually ships
Today 1
$247.75
Add to Personal List Quantity More Info

 

[Jerry/MT]

Using one large vent fan to vent two baths would be a better way to that.

Trying to exhaust air from two fan"s through a single outlet will give you some problems when only one fan is running. You might pump the air from one bath to another instead of out the vent pipe.And if you don"t get the exhaust pipe sized right, you can even have that problem with both fan"s running. Also the roof penetration will have to be larger.

 

[Dusty MI]

I inspected a house for my son that was vented under the eve that way. The humid exhaust air went right out the exhaust hood and up through the vented soffit into the attic and condensed on the roof nails that protruded through the roof sheeting and dripped into the cellulose insulation. You could see in the insulation where every nail had dripped.

Dusty

 

[buickanddeere]

Solid plastic is best. Metal suffers condensation and the rinky dink flexs hose is a waste of time.
On vent, one fan. A timer switch is a good idea.

 

[Jiles]

You should also consider the length of the run and make sure there is a check valve to prevent back flow to the other vent.
In the last three homes I have owned, all vents exited into the attic. There has been no noticable mold. They were vented into an open area. I can see how mold could form if the vent was directed onto a rafter or underside of roof.

 

[MarkB_MI]

I would not discharge directly into the attic. I've installed a couple of roof vent kits from Home Depot and they work well. You'll find them in the exhaust fan section; they're just a little doghouse that protrudes three inches above the roof. Less obvious than a pipe.

If you want to combine exhaust fans for two adjacent bathrooms, a better solution is to use a single inline fan pulling air from both rooms through a "Y". They aren't cheap, but they have the benefit that they're very quiet. You use two switches in parallel to control them. (You could use three-way switches, but you might not be able to tell when the fan's running.)

Here's a company that makes inline exhaust fans.
Fantech bathroom fans

 

[Steven-Id]

Here in Idaho code requires that bathroom vents go to the outside not terminate in the attic. I worked for a truss company and had an apartment building built 25+ years ago that vented into the attic. There was so much condensation that the moisture would freeze in the attic above the insulation. That freezing water created enough hydraulic pressure to literally push the truss plates out of the wood.

 

[Cliff (VA)]

I will add my support to Fantech. When we built our house four years ago we vented two bathrooms with a remote mounted Fantech fan and two timer switches in parallel. After I added a iris damper (you could use a butterfly valve also) to even out the flow it works great. Quiet too. You cannot even tell that the fan is on in one of the bathrooms.

I have inslulated metal ducts with short flex sections on either side of the fan motor. The flex sections help to dampen the noise from the fan. The fan motor is closer to the outside vent rather than the inside intakes. My metal Y came from Fantech.

I cannot say enough good things about my system. Works great, quiet as a church.

Good luck,

Cliff(VA)

 

[Crem]

A few years ago I helped my BIL check out a drip from his fan. We found out that the flexible pipe which went up and down along the way was filled with water in the low spots.
Below is a link to an article on bathroom fans. It looks like the pipe should be insulated with spray foam if the codes allow it.
Bathroom Fan Ventilation

 

[spacechem]

One comment about the central fan systems. They work, and they are quiet- too quiet. You may go away some weekend and return to find that someone has left the thing on and it sucked all the warm/cool air out of your house. That's why a good system will incorporate a timer- shuts itself off if you don't.

 

[Inno]

HRV heat recovery ventilator. It pulls moist or otherwise undesired air out of your house through an exchanger which pre-heats (or cools) the outside air coming in. It works very well. In our northern climate with low temps in the winter months condensation forms on the inside of the windows. Running the HRV takes care of it. You also do not need a kitchen or bathroom fan as long as you have proper ducting to these rooms. We have an extra cold air return in the bathroom and kitchen for this purpose.