I've had a Bosch LP tankless water heater for a decade now. What's always bothered me is that the ventstack is open to the sky (If I look up under the burners I can see a bit of skylight through the works (its a straight shot from burner to outside) Yesterday it got windy so i took a stick of incense and lit it. Sure enough the smoke gets drawn into the unit. (Of course it does right?) I thought maybe there was some invisible magictech I wasn't aware of that wouldn't allow that. How does that jibe with being green? Did the installer screw me and not put a proper (ie airtight??) cap on the stack? I know when its in use it needs to open, but still this just seems really cross-purpose. If that's the way its gotta be why do people think these are good appliances? Is there any solution to this?