Installing exhaust fan in place of Light

[jtfoxman]

I plan on removing my ceiling light in my bath and installing an exhaust fan/light combo. I can use the same wiring correct, and it will wire up basically the same way? I plan for the fan to come on whenever the light is on. The exhaust tube will go up into my attic and my soffit is about 3ft away. Would that be the best place to exhaust it? And should I run it across the floor or elevate it. Flexible or rigid duct? What type of outlet hole in the soffit to prevent anything from getting in through it. My attic is unfinished and unheated. Should I have any freeze worries in the duct or insulate it. My attic gets cold but not extremely cold.
Sorry about the winded post.
Thanks!

[Kman]

There are probably two hot wires and one neutral, and one ground. One of the hot wires is for the light, the other for the fan. Both of them will connect to the switch leg, unless you happen to have two separate switches for them.

I've always used flexible ductwork for mine, and three feet is not to far to run to the soffit. I wouldn't worry about it freezing. Is your soffit vented? If so, just aim it toward the vents.

I wouldn't elevate it, since water will condense in the duct, and likely run back down through the fan. It's a good idea to leave the fan running for a few minutes after the steam clears out of the room to help dry out the duct.

[pushkins]

Lowe's and HD both sell a soffit mounting exhaust duct, that way the condensation is directed to the exterior of the home. The exhaust duct has a built in flapper that closes when the fan is not in use. Steam rises so if you only direct it to the soffit the steam makes it to the area then tends to rise up against the roof decking. Soffit vents are designed to suck air IN.

[jtfoxman]

Thanks for the advice!