Bathroom fan exhaust vent

[CMV]

Replaced my builder-grade, plain plastic loud bathroom fan with a lighted one a few yrs back. Well, it's getting rusty and looks like a turd so is getting replaced again soon. When I put 1st one in, I noticed it just vents between the ceiling and 2nd story floor. There is a vent on exterior wall, but nothing ducts this fan nor the other one in the tiny little commode closet part of the bathroom to that vent.

Should these fans just discharge into the empty space between ceiling & floor or should they be ducted to that vent to exhaust directly outside? It's the way house was built so I just left it that way, but have wondered about it ever since. Doesn't seem like the fan by the shower should be sending that moist air between the floors. The vent on exterior wall is probably straight line distance 8-9' from either fan.

While installing fan the 1st time, I noticed I could see a lot of daylight from the exterior vent cover, so I guess there is some breathing going on between the floors. I didn't see any signs of moisture, mildew, water damage, etc - looked normal. But house was only 5 y/o at the time. Anyway, just wondering if that's normal/acceptable that bathroom exhaust fan just vents into open space between the floors or if it should have some sort of duct directing that moist air directly outside?

 

[LouNY]

I do believe it should have been ducted.

 

[teejk]

Sounds like somebody short cut the venting (maybe they forgot to do it before the sheet rock was up). Also sounds like they made it appear to be vented outside to get past inspection. That much moisture is not a good thing (mold, etc.).

 

[RNeumann]

Yes it should be vented to the outside. It’s worse to vent that into the floor cavity. Seeing daylight isn’t good either. Most of that stuff can be sealed from the outside.......it’s not the best but it it’s better than nothing.

 

[EddieWalker]

Yes, it should be vented. Are they always vented in every house? no I used to be very paranoid about this, but over the last couple of decades, it's so common that I no longer even pay attention to it in homes that I'm working on. I have never seen any moisture issues or mold from a non ducted vent. I personally install the ducting because it's simple and that's how it's supposed to be done, but I wouldn't lose any sleep over it if there wasn't a duct, or if it just goes up into an attic and not outside.

Do you see any sign of moisture or mold?

 

[3Ts]

It's supposed to be vented to the outside. There are building codes covering this along with what size of duct is supposed to be used based on the fan's cfm and length of duct.

 

[KennyG]

Not surprising. I found one not vented to the outside when I remodeled my house. Took a bit of work to snake a vent through and fix it. As an aside, when we remodeled we took the contractors advice and got Panasonic vent fans. They are almost silent and well worth it. I cringe every time I go into an expensive house and hear the economy grade fans.

 

[kcflhrc]

You will find the majority not vented to the outside. I have yet to see an issue with it.

 

[jk96]

+1 on Panasonic bath fans. We had a lightning strike on our home that took out all of the bath fans in the home. If you ever have to replace them Panasonic retrofit fans are really slick the way they install. Makes it really simple to replace the existing fan.

 

[jk96]

Also if you want to help with backdrafts from the vent to outside install a backdraft damper inline of your ducting. These work much better than the ones you see as part of the bath fans.

RSK4 - Fantech RSK4 - RSK Series 4" Duct Backdraft Damper