The Tucson Institute for Sustainable Communities is a non-profit educational organization based in Tucson, Arizona, which works to cultivate vital and sustainable communities that are resource efficient, ecological, affordable and equitable. Sustainable Sources 1994-2001. Gas water heating for domestic hot water can be engineered to provide space heating as well as water heating. Several high efficiency models are available that allow venting of the water heaters through a wall instead of a chimney. Electric heating is not involved permitting a reduced electric panel size.
Less space is needed compared to two separate systems.
The air handler can be located to minimize ductwork. The combo system circulates hot water from the water heater through a heat exchanger in the air handler. A blower will move the heated air through a standard duct system. In the summer, an air conditioner is connected to the exchanger and the system functions similarly, with cool air being pushed through the ductwork. The pollutant levels created by natural gas combustion are less than other conventional water heating options except solar.