JD. Most city codes and all Mechanical codes prohibit venting into the attic. Two of the most damaging things to shingles are mositure and heat and you're putting both into the attic. Ever drive around and see a roof with about an 8 foot circle of shingles curling up? Dryer venting into the attic, every time. Venting to the soffit, if that's your only option, would be better than venting into the attic, in my opinion. However, the more bends that are in the piping leading to the soffit vent and the longer it is, the less efficient the fan is going to be. Having said that, I see bathroom vents in the attic in almost every house I have inspected or worked in or on. And they have had no problems with moisture. If you're not running the fan 24/7 you won't be putting that much heat or moisture into the attic, if the attic is properly vented. I never use our vents for moisture in the bathrooms, frankly, I'm thankful for the humidity since we have gas heat. Was that confusing? Hope it helps anyway.