I plan on installing a unit heater with a 4" exhaust duct which will be exhausting some heat, along with the products of NG combustion. It is going to be installed in the garage, and I have the option of either going through the garage wall (wife thinks this will look ugly, but it would be much easier), or through the attic and out the roof (5" of snow presently).
Is there any advantages to one or the other? If I decided to exhaust through the wall, the vent would be very close to the soffit. Even if I meet minimum clearances, are there concerns with this carbon monoxide/smell/heat going into the attic.
Yep. Along with a LOT of water vapor which is really what most of the exhaust is made of. It will probably discolor the siding/soffit and get the wife mad at you. I would go vertical. If Momma ain't happy nobody is happy. (According to Dr.Phil).