I'm not sure it's lame-o; you're at least thinking about things.

Depending on how tall your house is, you might get a pretty good head, but I'm not sure you would get all that much flow. I must say, listening to it pour outside this morning, it is a very enticing idea, though.

Our house is pretty tall -- 3 stories with the bottom floor having a 2.7m ceiling, second floor a 2.4m ceiling, top floor a 2m ceiling that slopes to 0. There is about 40cm of basement above the ground level on average, so I would expect a head of 5.6m -- not horrible, but not tremendous.

Flow is going to depend on climate and roof size. Our roof is kind of small -- the house has a footprint of about 9m X 7m roughly, and is L-shaped, so that's not full. It's raining like a bitch right now, but that's pretty rare. If you put a 2cm/hr rainfall on top of that, you can expect 1260L/h of flow.

In southern climates (e.g. Florida, Georgia, Alabama, etc), it tends to rain quite a bit harder and more frequently than up here in New York, but the buildings tend to be lower to the ground, so it might be a wash (no pun intended). I'm not sure what you get for rain out there in Wisconsin or how tall the houses are, or more to the point, how tall your house is.

I moderate another tribe, Renewable Energy and Solar Power; you might want to throw the question out there, also. There are some folks in that tribe who are much smarter than I. The link to it is tribes.tribe.net/altenergy