Bathroom exhaust fan AND laundry vent question

Richard · Jan 28, 2006

Setup: Utility room going to be made into a full bath. It's already plumbed for shower/toilet/sink.

Room is roughly 16' wide by 14' deep with 9' ceilings.

Washer/dryer are on back wall, just offset to the right of being in the middle. Dryer exaust vent from the dryer itself (rear discharge from dryer) goes to the right on the ground maybe 4' and then goes up to the ceiling where it discharges outside. (this is block wall and is all under grade so had to go UP to get it outside)

Ok, wife bought exhaust fan for the bathroom. This thing has an 8", yes EIGHT inch outlet /forums/images/graemlins/shocked.gif

I might see if I can step it down the the same size the dryer uses (I think it's either 4" or 6"?)

None the less, here's my thoughts

Take out the plastic (with wire), dryer vent and replace it with hard ductwork. Put the bath vent in and step it down to the same size used for the dryer.

Bath vent will be near middle of room, perhaps a bit skewed to the back/left side. Anyways, take the pipe from the BATH vent to the back wall, cut it 90 degrees to the right to run parallel along the wall the dryer is on. When the bath vent meets up with the dryer vent coming up from the floor, install a "T" there and allow BOTH items to blow out the same flapper on the outside of the house.

Any thoughts on why I might NOT want to do this??

Any thoughts are appreciated!
/forums/images/graemlins/smile.gif

DocHeb · Jan 28, 2006

The air will follow the path of least resistance - and that may mean that either the dryer or vent fan may exhaust out the other appliance's duct back into the room, rather than to the outside. You could use backflow preventors in each line, but it just isn't the right way to do things. They should have separate exhaust ducts.

Any bath vent fan that has an 8" duct is a monster. You may have make-up air-flow problems as the bath fan may pull air back through the dryer vent. Again, this may be decreased by backflow preventors, but it could be a problem. Is the bath fan oversized for the room? Typically bath fans are sized to allow 8 changes of air an hour. Multiply room length x width x height (in feet). Divide this number by 8 to get roughly number of cubic feet per minute you fan should pull.

Consider putting the bath vent fan on a rotatory timer. Intermatic makes a timer that fits within a standard box with a switch plate, and can be set for 5 - 60 minutes. Very handy in clearing a bathroom out "after-the-fact."

Richard · Jan 28, 2006

I'll go see if I can get a quick pic of the corner so it's clear (although you seemed to get it)

I'd say yes, this is oversized based on what the wife told me. (somewhere in the instructions I saw it was rated for continuous use??? I mean... am I THAT bad? /forums/images/graemlins/blush.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/blush.gif)

I might add, my only REAL concern is to remove the moisture from the shower as opposed to any other air removal. This room is under grade on 3 sides, with the 4th side opening up to the inside of the house. It won't get a lot of exposure to the outer elements.

Farwell · Jan 28, 2006

I agree with not putting the bathroom and dryer vent through the same duct. You could possibly do a duct inside a duct. 8 inch outer pipe for bath room and 4 inch inner duct for the dryer. Or you could do a side by side.
I have had an eight inch fan in a bath with a moisture problem that was a direct through the wall to the outside world and it worked great. I ran it only while the shower was running or when the toilet was being used.
I didn't do the math but the size of your laundry/bath room sounds big enough to need an 8 inch fan to vent it properly. Your room is as big as many master bed rooms, wish I had that much space.
Farwell

CurlyDave · Jan 28, 2006

Give some thought as to how air will enter this room in order to be exhausted by this mighty fan.

For instance, if the door opens outward, it will spontaneously close with an authoritative "thunk" when the fan is on.

16' x 14' x 9' is a very large bathroom, some people are uncomfortable in a bathroom that large. It is instinctive to want concealment when we are in a vulnerable position. Is there a way to build a partition to separate the bathroom from the laundry room? This would actually make both rooms more comfortable.

If you cut the bathroom down to a manageable size you could return the fan and get a much more modest one which would do the job.

Richard · Jan 29, 2006

</font><font color="blue" class="small">( Give some thought as to how air will enter this room in order to be exhausted by this mighty fan.

For instance, if the door opens outward, it will spontaneously close with an authoritative "thunk" when the fan is on.

16' x 14' x 9' is a very large bathroom, some people are uncomfortable in a bathroom that large. It is instinctive to want concealment when we are in a vulnerable position. Is there a way to build a partition to separate the bathroom from the laundry room? This would actually make both rooms more comfortable.

If you cut the bathroom down to a manageable size you could return the fan and get a much more modest one which would do the job. )</font>

C'mon guys... this is the wife designing this... I got NO say ! /forums/images/graemlins/tongue.gif

The dimensions of the room are gross dimensions. The depth of the shower will cut into the size of the room. The washer/dryer will be behind a (currently being built) wall and on the right side of room, another closet wall will be built. That will cut the 'apparent' size of the room down by 3' on two adjoining walls.

She told me last night, she wanted to build a false ceiling above the shower as you're not 'supposed' to have a 9' ceiling in a shower. This is ok by me as that now allows me to have ANY kind of fan above the shower but more importantly, I can now duct it THROUGH this ceiling space above the shower to the OTHER side of the room and vent it directly outside!! Seems the dryer vent might no longer be an issue insofar as it relates to this fan.

The doors into the bathroom/utility room are going to be 36" wide french doors. I'm not sure if that's so I can make a grand entrance INTO the bathroom /forums/images/graemlins/crazy.gif or a grand entrance OUT of the bathroom when I'm done /forums/images/graemlins/confused.gif /forums/images/graemlins/blush.gif

CurlyDave · Jan 29, 2006

The doors into the bathroom/utility room are going to be 36" wide french doors.

French doors are the ones with panes of glass from top to bottom. Maybe this is to provide a better view of the activities in the bathroom... /forums/images/graemlins/confused.gif

jimmysisson · Jan 30, 2006

The make-up air is going to be a problem. The bath fan will suck air through the dryer, since the doors probably don't leak enough air from the rest of the house to make up for what's being exhausted. However, if you can restrict the outflow of the big fan you will reduce its cfm rating, without hurting the fan any. (careful of duct whistling, though). EFI has a couple of products you might be interested in. One is a switch that runs the fan and light separately, so the fan can run for a (preset) time after you shut off the light when you leave, very helpful. Another is a dryer vent termination that shuts tighter than the usual hood/flap, yet opens enough so there's no restrictions. I'm pretty sure it's not rated against backdrafting, but is probably better than a flap. BTW, if the dryer is running and someone starts the non-restricted 8" fan, you'll probably backdraft even the lint screen and end up with a mess. Good luck getting in charge of the engineering here. EFI site is www.efi.org Fan switch is 5500.501, termination is 4510.51 This is a good place for energy efficient products.
Jim

Richard · Jan 30, 2006

We're going to downsize the exhaust fan. When she bought it, she saw "big bigger & biggest" and grabbed the largest one she saw.

She DID ask me to post the following question to help settle our "argument"

I told her we should install the fan DIRECTLY above the shower and essentially, in the shower stall (in the ceiling of course).

She thinks it would be better OUTSIDE the shower stall so it will catch the steam as it cascades out the shower door opening and flows up to the ceiling.

I came back telling her, (mind you, we're going to have some arched doorway into the linnen closet, chandeler light...)

Anyways, I told her since she's so skewed to the visual spectrum, that she'd probably rather have the exhaust fan "hidden" by virtue of being in the shower stall instead of just down the ceiling, from her fancy light fixture.

She thinks I'm all wet (that people do NOT put exhaust fans directly in the shower stall)

Any opinions/facts/other on that idea??

I tried to get some pics over weekend but pc at home didn't let me upload them, I'll try to attach them here

(forgive the mess)

Richard · Jan 30, 2006

here is pic of the dryer vent. I can NOT vent it out any lower as it's all below grade. I'm going to swap out the flexible stuff for some hard ductwork.