Bath fan exhaust venting

Users who are viewing this thread

Johnny K

New Member
Messages
1
Reaction score
0
Points
0
Monkeyboy.. please keep us posted on what you end up doing.. I'm in the same boat..

We have large master bath with a high vauletd ceiling.. in the bath room there's a seperate toilet room that has a window and an exhaust fan mainly for light and for the riddance of any foul odors :eek:

Well the vaulted ceiling collects the steam and moisture from the shower (wife takes really long ones.. not sure what's going in there, but that's another story..) We've started to develop small black spots (mold) on the textured ceiling..

So I bought a fan for the main bath area (130 cfm), tapped into electric for the light above the shower. I also ran the flexable ducting down to tie into the venting used for the one in the toilet room... I couldn'y find any Y's made for such an application, so I got a 3" (i.d.) pvc connector that had a straight thru piece and a curved connector coming in.. used large screw clamps to make sure it all good and tight..

Problem now is with the new bathroom fan on, and even though the toilet room fan has the flap in there to stop air from coming in, there's enough gaps in the flap for air to be pushed into the smaller fan (path of least resistance).. the run for the new fan is about 15 feet of ducting before it hits the pvc connector and about a 2 foot run from the pvc connector to the toilet room fan and 2 foot to the outside vent..

If I can't solve it now, I'm tempted to vent the toilet room fan to the attic and use the exterior vent for the new bathroom high volume one that will be used during and after showers.. when the toilet room fan is on, the door is usually shut and little or no moisure is present (again it for odors) and if a shower is taking place, the main fan will be on.

Anyone have any feedback or suggestions... if I vent the one for the toilet room to the attic, it makes sense to have the venting pour into an open area and higher up in the roof space (no directly into any insulation).. the attic space is huge (could dry wall it and live up there if someone wanted to).. a roof vent isn't a good option as it's 2 stories up.. if we hever get any roof repairs done, I'll install a vent then and be done with it..

Thanks for any suggestions!!

Johnny K
Cleveland, OH
 

JDkimes

Engineer
Messages
199
Reaction score
0
Points
16
Location
Littleton, CO
A lot of building codes require either a bathroom fan or a window that opens, since the window that opens is cheaper a lot of builders don't bother w/ a fan. But unless you can get the person showering to open a window quite a bit in the middle of the winter it's not going to get the moist air out and then you get mold and or mildew.

Some places also allow or did allow a vent to the attic. But as has been noted you're only moving the problem to a different part of the house if you do that or vent to the basement. Go up in an attic in cold climate in the middle of winter in a house with a fan vented to the attic and you'll see icicles hanging from the nails and other places. Then you'll have mold and mildew in the attic (or basement). You've got to get the moist air out of the house. Even venting just the toilet room to the attic is probably not advisable, all the air in the living space is moist and it will condense in a cold attic, except maybe in a place that's dry and warm all year. Consider the condensation on a single pane window in a bedroom in the winter, same thing will happen with any air from the living space into the attic.

Joining two vent pipes is a tricky deal that involves balancing flows etc and that might involve installing a couple of different dampers to prevent back flow as has been noted here. As with most things doing it right is usually not the easiest way. The easiest for you might be closing off the line to the toilet and installing just a high volume exhaust in the shower area. It will draw air from the toilet room for some odor relief, assuming that they're adjoining. Or probably better just bite the bullet and put a new fan in and vent it out the wall or the roof it's really pretty easy. You could probably do it in an afternoon if the wiring is available. Working around the insulation is a hassle and you have to be able to get to the outside of where ever the holes is. But check "This Old House" or this
Black and Decker

You could install an inline fan in your existing joined ducts like this
to suck the air through instead of pushing it and that would eliminate some of the balance and back draft problems. They're a little more expensive and probably no easier to install than the regular ones, but they're usually higher quality and quiet and might eliminate the need for new holes for Johnny K that has existing toilet fan.


As for weather tight you will get some backdraft but it's better than mold in my opinion and no house is air tight. The air comes in for the furnace, water heater, and out for the stove, dryer, and lots of other tiny holes.

Any way that's the opinion of a lowly mechanical engineer.
 

PEW

DIY Senior Member
Messages
484
Reaction score
0
Points
16
A roof vent is not that hard to put in, and done correctly leaking is not a problem. I have done many of them, in my oppinion they are easier than a side wall installation. The only down side is that snow and ice can block it for a while during the winter, if you are in a cold area.
 

daveydo

Member
Messages
36
Reaction score
0
Points
6
Location
Nova Scotia
To address your concerns about heat loss due to venting your fan to the outside. It is well known that heating moist air is much much harder than heating dry air. So, by venting the moist air out of the house you are making the building easier to heat.

Further, mold is nothing to take lightly. It can cause many serious health problems. By venting into an attic or basement you would be promoting wood rot, insulation damage, higher heating costs and mold growth. In short, it is a very bad idea to vent moist air into another part of the building.
 

mjwolsky

New Member
Messages
2
Reaction score
0
Points
0
Bathroom fan makes popping sound when windy outside

The exhaust fan in my upstairs bathroom makes a popping sound every 5 seconds or so when it is windy outside. I'm assuming that this is caused by changes in air pressure lifting and then dropping the backflow preventer flap. Is there an easy fix for this problem? The exhaust tube goes up, then does a 90 and exits on the side of the house. Thanks for the help!
 
Last edited:

JDkimes

Engineer
Messages
199
Reaction score
0
Points
16
Location
Littleton, CO
It doesn't sound like that big of a deal but a couple of possilities:
1. Put some sort of foam rubber weather strip at the seal of the damper to cushion to cushion the closing.
2. Change the outlet of the vent on the wall with one that has a spring loaded damper that might help keep it closed during the windy days
3. Put one of the outlets on that is more of a louvered damper those don't seem to slam.
4. It might be as simple as making sure the door to the bathroom is closed during windy periods to prevent the quick pressure swings between outside and the bathroom. Of course if you live in Wyoming or someplace like that everyday is windy.

The problem might be that the damper that is slamming is actually the one that is a component of the fan. It's at the outlet of the fan into the duct. That might not have an easy fix but keeping the bathroom door closed would help that.
 

mjwolsky

New Member
Messages
2
Reaction score
0
Points
0
Thanks for all of the suggestions. I think the popping sounds might be coming from the damper that is built into the fan because it is a fairly loud and solid noise...the outside vent is just made up of 4 or 5 light-weight plastic flaps. I tried taking the fan apart but the ceiling is sheetrock and it's difficult to get anything done...I'd probably have to go up in the attic and see if I could get to it from there. Do you think a rubber seal on that damper would help? I'll try keeping the door shut and see if that helps. I live in ND so finding another windy day shouldn't be a problem. =)
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks