Running A Waste Line in an Exterior Soffit???

I live in a cape style house and I am finishing off the upstairs. I'd like to put a bathroom on the second floor. However located the new bathroom over the existing on the first is impossible with the sloped ceiling on the second floor. So I would like to put it in one the dog house's on the second floor. Here's the question, can I run the second floor main in my soffit/eve and box it out with insluation and plywood inside of the soffit from the bathroom to the main? The house is on a slab and the main is below the slab so I will have to break up some concrete to connect the two. I attached a sketch. Any help would be greatly appreiciated.

Program

What program did you use to make this drawing

AutoCAD 2005

I'd be concerned about freezing, insulation or no. Maybe lay in one of those plug-in heat strips under the line.

Thanks Mike, but I heard that the heat stips are no good in enclosed spaces...fire hazard. The line wouldn't be full of standing water though, that's why I think it may be possible. I don't know that's why I'm asking.

Insulation does not heat or cool anything. If water is not moving and the temperature drops below freezing far enough that the space where the pipes are goes below freezing, insulation will only slow the process and the pipes will freeze. You might look into providing heat into the space as opposed to wrapping the pipes. It doesn't have to be very warm, just above freezing.

Maybe insulation will prevent the scenario I was thinking of: It was a dark and stormy night, about 20 below. As the homeowner started brushing his teeth on this frosty morning, the waste water started running down the frozen PVC pipe, and quickly froze, forming an ice dam. The rest of the story is not pretty, since he was headed for the toilet...

PS: just read Gary's post -- the "maybe" my first sentence assumed a warm environment on the other side of the insulation that might prevent the temperature from dropping too far in the insulated space. The soffit area doesn't strike me as a particularly warm place, though.

Hey Mike thats a pretty shitty thing to say LOL!