Furnaces are more energy-efficient than ever
Recent regulations for furnaces are making them more energy efficient than ever. Furnaces are rated by annual fuel-utilization efficiency (AFUE). This is the minimum percentage of fuel that is consumed in the process of heating your home. The rest escapes through the flue. Gas furnaces made in the early 1970s may have AFUE ratings as low as 56 percent; modern furnaces have minimum ratings of 78 percent (for oil), and as high as 99 percent for gas. That means replacing an older furnace can make a significant dent in your fuel bill.
How a Furnace Works
Inside a gas- or oil-fired furnace, the fuel is mixed with air and burned. The flames heat a metal heat exchanger where the heat is transferred to air. Air is pushed through the heat exchanger by the “air handler’s” furnace fan and then forced through the ductwork downstream of the heat exchanger.
At the furnace, combustion products are vented out of the building through a flue pipe. Older “atmospheric” furnaces vented directly to the atmosphere, and wasted about 30% of the fuel energy just to keep the exhaust hot enough to safely rise through the chimney.
Current minimum-efficiency furnaces reduce this waste substantially by using an “inducer” fan to pull the exhaust gases through the heat exchanger and induce draft in the chimney. “Condensing” furnaces are designed to reclaim much of this escaping heat by cooling exhaust gases well below 60°C, where water vapor in the exhaust condenses into water. This is the primary feature of a high-efficiency furnace (or boiler). These typically vent through a sidewall with a plastic pipe.
Heating system controls regulate when the various components of the heating system turn on and off. The most important control from your standpoint is the thermostat, which turns the system — or at least the distribution system — on and off to keep you comfortable. A typical forced air system will have a single thermostat. But, there are other internal controls in a heating system, such as “high limit” switches that are part of an invisible but critical set of safety controls.
Furnace Buying Guide: We Help You!
What the best furnace has:
- The proper AFUE rating
- Two stage valves
- A programmable thermostat
- Sealed combustion
- A long warranty
What you should know know before you go:
- Should I repair or replace?
- Is my home energy efficient?
- Are you prepared to maintain your new furnace?
Most Fuel Efficient Furnaces
The best gas furnaces and boilers today have efficiencies over 90%
The efficiency of a fossil-fuel furnace or boiler is a measure of the amount of useful heat produced per unit of input energy (fuel). Combustion efficiency is the simplest measure; it is just the system’s efficiency while it is running.
Currently there are no Energy Star Rated Furnaces available in Canada.
For assistance, install, or ordering, contact us.