Many of the newer efficient furnaces use power-vent technology. Houses that don't have chimneys can use gas furnaces and water heaters with power-vents. These appliances are usually recognized by the (usually white) plastic pipe exiting the top of the appliance that vents to the outside of the house. It uses a special fan to vent the spent fuel byproducts to the outside of the house. I don't know whether a power-vent can be adapted to an existing furnace, especially if it was not designed to use one. The power-vent furnaces are so efficient that the spent exhaust gas is not very hot when it reached the power-vent fan. If you mounted the power-vent fan onto an old furnace, it may produce too much exhause heat and melt the fan. You could always buy a new furnace that uses power vent technology. I don't know the age or condition of your existing unit? I know that power-vent water heaters run about $900 versus traditional water heaters that use a chimney run about $250.
First, find out whether your existing furnace is designed to be power-vented. Then, go from there.