I am in the process of building a series of condos, and thinking about what kind of heat to use in them.  Right now, the front-runner is a Trane Gas Furnace.  Each of the buildings will have their own unit, so I need something that works in a residential unit, rather than a multiple-unit boiler.  Gas seems to be the way to go right now, because as much as I’d like to invest in solar energy or some such, I just don’t have the cash, and I can’t raise the price of the condos any more because of the housing market being the way it is.