Furnaces

The Condensing Gas Furnace

Condensing gas furnaces are the most energy-efficient furnaces on the market today. They are an ideal choice as a new or replacement furnace for virtually any home serviced by natural gas or propane. Here is why:

  • Condensing gas furnaces have an annual fuel utilization efficiency (AFUE) of between 90 and 97 percent, compared with AFUEs of about 60 percent for old furnaces and of 78 to 84 percent for standard efficiency units. (AFUE is the yardstick for rating furnace efficiency.)
  • Because of their increased efficiency, condensing gas furnaces use, on average, 33 to 38 percent less energy than old models and 10 percent less energy than a standard efficiency model. This helps conserve Canada’s natural resources and reduces harmful environmental emissions that contribute to climate change, urban smog and other air pollution problems.
  • Any extra cost associated with purchasing a condensing gas furnace will be quickly recovered through energy savings. For example, a homeowner with an old gas furnace could save about $300 a year by switching to a condensing gas furnace with an AFUE of 96 percent.
  • Condensing gas furnaces are available in a range of sizes. They can be installed in the same location as the furnace that is being replaced, by the same technicians and by using the same ductwork.

How the technology works

In a furnace, combustion gases generated by the burner pass across a heat exchanger and release heat before being exhausted to the outdoors through a chimney. High-efficiency furnaces use additional heat exchange surfaces made of corrosion-resistant materials to cool and condense the combustion gases (causing them to liquefy), thus releasing more heat for the home. The small amount of wastewater produced by this process is piped to a floor drain.

This condensing process has another important benefit. It reduces the temperature of the flue gases to the point where they can be vented through a PVC or ABS plastic pipe out a side wall of the house. This eliminates the need for a chimney, which is a major source of heat loss in homes with old furnaces.