bathroom exhaust fans

[coltrane]

I would like to put exhaust fans in 2 bathrooms. should these fans exhaust out the roof or can they just exhaut into the attic?

thanks

john

[JoeSpareBedroom]

Roof only, and preferably through vents made specifically to accept the type of duct normally used for such fans. The previous owners of my house did sort of a hack job, using coat hanger wire to attach the duct to a normal roof vent. Somehow, this hasn't caused problems, but when I re-roof soon, it'll be fixed anyway.

[HeyBub]

They should vent to the outside else you could have moisture problems in the attic.

I say "outside" instead of roof because it is also possible to vent to a soffit or wall.

[Mark K]

You don't want the moisture venting into your attic. You can vent to the roof, or even the soffit. Either one will do the job.

Mark

[coltrane]

thanks to all. now I have to get the guts to open my roof

cheers

[Mikepier]

If you don't have the guts like me, you can run the ductwork close to a vent in the roof. I have an attic fan, and I ran my exhaust duct close to the vent. I know this is not the correct way to do it, but I did not want to risk any leaks by opening up my roof.

[TH]

If the bathroom doesn't have a shower/bath then going into the roof would be OK since you're not venting any moisture. I just put to bathroom fans in my house, I just had a roofer guy install the vents. I bought them at Home depot and he just charged me $75 to install them.

Some tips when doing this.

1. Over size the fan. If the chart says 80 CFM go with at least 100 You will never be sorry that your fan works too well. It will also let you have longer ductwork and reduce the possibility of getting condesation drips. I put a 110 in a 8x8 bathroom, and the shower can't even fog the mirror.

1. Use a timer instead of a switch.

2. If you have a roofer install your vent, get up on the roof and mark were you want the vents, or be there when he's installing them. My roofer, despite detailed drawings and measurments, still managed to put one vent in the wrong spot, which made me use a lot longer duct length, but still seems OK.