We're considering ways of heating a large finished garage that is used frequently as a home business office and shipping room. We have the gas forced air furnace and hot water heater in the garage and would like to use natural gas for heating versus electric. We'd like some input on the best way to go. One suggestion that came up that I'd really never thought of before was putting a circulating loop off the domestic hot water heater. I've seen a lot of ventless heaters on the web, but don't know if I'm comfortable with that in a dwelling. Can a new gas heater exhaust be cut into the flue for the existing furnace? Any thoughts? Luck, Kizmet