The Mechanics Behind High Efficiency Furnaces

High Efficiency Furnaces

Life spans of furnaces vary, but for most units, 15 years is a safe average. People that have installed heating systems in the early 1990s will soon be due for furnace replacements. Because the technology driving HVAC systems has drastically improved in the last decade, we spend a lot of time educating our clients on the mechanics of high efficiency furnaces and how they differ from conventional heating units that they are used to.

Measuring Efficiency
Furnaces use the AFUE (Annual Fuel Utilization Efficiency) rating to measure how efficiently a furnace utilizes fuel. The AFUE is listed as a percentage of how much fuel can be converted into usable heat. The more efficient a heating system is, the more heat per unit you will get from your fuel.

For example, a furnace that has a 90% AFUE converts 90% of its fuel to heat, and 10% is wasted (lost through the exhaust). Furnaces from the 1950s typically had an AFUE of 50-60% — meaning that as much as 50% of a furnace’s fuel was wasted. Current Canadian government legislation mandates that most residential furnaces have a minimum efficiency level of 90%.

Conventional Furnaces
The basic principal of a heating system is simple:


  • Your thermostat signals the furnace to produce warm air
  • The gas valve opens, delivering fuel to the heating systems burners
  • Pilot light/electronic ignition ignites the burner in the combustion chamber
  • Heat is created in the heat exchanger
  • Warm air is pushed to the plenum (air space chamber) and then circulated throughout the home
  • Condensed gasses created from the combustion process are vented through the exhaust stack

High Efficiency Furnaces
The innovation of high efficiency furnaces comes in the last stages of the heating process. Instead of venting the gasses created from combustion, high efficiency heating systems employ a second heat exchanger to convert the condensed gasses into usable heat. With this secondary heat exchanger, virtually all the fuel can be turned into usable heat.

Team Harding is proud to carry only the best high efficiency furnace brands and employ certified, professional technicians to perform all our installations.

Contact us today if you’re ready to replace your old heating system, to learn about the different products we offer or for help choosing which unit is best for your household.

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