ideas of venting a bathroom fan in attic

david szela

Hi im about to finish my attic remodel and i have read several posts on the chatroom about venting . I dont want to go thru my roof and ive read not to do that because of moisture coming back into bathroom. Ive also read not to vent thru my soffit cause it can cause damage to the roof plus mold and moisture issue under eave . I havent heard to much negativity for goin out the side of the house which i can do. any input would be great. thank you Dave

jklingel

Through the roof is the safest. You won't have water problems if it is done properly. Going out the side may not get moisture away from the house, esp if you are near the eaves.

Beepster

Going through the roof is A-OK. You must have misread those posts.

Is there anywhere you can tie in with an existing vent that already goes through the roof? Punching a new vent through the roof should be a last resort.

B

4just1don

just wondering cause I dont know. Can you tie it into the plumbing stack vent?

TarheelTerp

No.
This will require a separate hole in the roof, properly flashed of course,
for the vent housing to be installed. THEN you can attache the vent hose from the bathroom(s) to that.

hth

below is a nice picture of such:

Attached Images

 

Beepster

Ohhhhhhhh, you are talking fan vent, not DVW vent...what he said.

david szela

the problem with going thru the roof that i read was that the condensation will go back down into the bathroom / fan because the vent is directly above it and that is true because it happened to a friend of mine .maybe if there is a bend or not just straight above it. it wouldnt be a problem. he does have an older fan

TarheelTerp

a) it's not an issue
b) if you think it matters then do the side wall vent option

mae-ling

My last HVAC guy said the best was to go down an interior wall and out the floor joists. Said cold air could not come up it. Also insulated where it was in the floor joists. Not always possible in renovations.

Gary in WA

Be sure the ducting is insulated and supported well. The elbows need foil tape on each segment, even the unused ones. (The cheaper elbows tend to fall apart wetting your attic insulation....). Use a few 45's right at the start to gain any needed pitch in the longer run as said. I can remember 4-5 mentions (here) of the condensation problems with roof exhaust...and duct was insulated. Insulate the fan box itself.

Gary

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ddawg16

The LAST thing you want to do is put warm moist air in your attic.

If the fan does not have enough velocity, I could see how maybe that might happen.

Insulating the pipe in the attic would help cut down any condensation in the pipe. Of course, a side exit would be your best option to eliminate condensation coming back.

If your looking for a fan now, pay attention to the CFM and Sones (noise). There are charts out there that suggest what CFM you need for a given size bathroom. And getting a quiet fan reduces the irratation factor. I personally hate loud bathroom fans.

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