RENO EXPERT: Figuring out Furnaces

Figuring out Furnaces: Understanding the key features for apples to apples comparisons

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Figuring out Furnaces: Understanding the key features for apples to apples comparisons

New units with all the bells and whistles are much more efficient than older models.

It’s Murphy’s Law that your furnace will conk out right when you need it most, in the coldest depths of winter. You wake up to a freezing home and start your day trying to find a technician who can come in ASAP, meaning you’re not really in the position to properly research what you need.

If you have a furnace that’s more than a decade old, replacing it should be somewhere in the back of your mind. Here’s an overview of the key features to look for when the time comes that you’re forced to buy a new one.



The key operating stat to look at when comparing furnaces is each unit’s annual fuel-utilization efficiency (AFUE) rating. This calculates how much of the fuel used is converted to heating energy, so the higher the number, the more efficient it is. The current Ontario Building Code requires a high-efficiency condensing furnace with a minimum 90 per cent AFUE. Today’s top-of-the-line furnaces have AFUE ratings of 98 per cent or higher.

If your furnace is a really old conventional model that vents up the chimney, you’ll have to replace it with a condensing unit. These models vent horizontally out the sidewalls, so you’ll need to run PVC vent pipes. You’ll also need to run a drain line for condensation to the sewer.


The heating output of a furnace is rated in British Thermal Units, or BTUs. Don’t just assume that you should replace your old furnace with the exact same size as your existing one. If your home has been extensively renovated with an addition or updated basement, you may actually want a larger unit to provide even heating throughout the home.

But new units with all the bells and whistles are much more efficient than older models. If you’ve upgraded your windows and doors, boosted the insulation in the attic, and made other energy efficiency improvements, a smaller model may be more appropriate as it will cycle on and off less frequently. An HVAC expert can calculate the requirements based on the size of your home.


The blower motor is, obviously enough, the component that pushes the heated air through your ductwork. Consider upgrading from a single-stage blower to a two-stage or electronically commutated motor (ECM for short). Single-stage blowers operate at full capacity all the time. Two-stage units operate primarily at the lower stage, only kicking in to the second one on the coldest days. They cost more upfront, put you’ll recoup that money in long-term savings on energy consumption.


Unless you have a really old mercury thermometer, odds are that by now you’ve upgraded to at least an early generation “setback” thermostat that enables you to program different temperature settings for different times of day. But the latest “smart” thermostats can do a lot more than that, including enabling you to remotely raise and lower the temperature from your phone. Many also allow you to save energy by creating heating zones with reduced temperatures in little used parts of the home. Models such as the Nest actually learn your habits and adjust things accordingly, and can also be tied in to home security cameras, smoke and CO detectors, and more.


If your furnace needs imminent replacement, Ontario’s hydro companies are offering rebates on furnace upgrades, including $250 for installing a model with a variable-speed ECM motor. The catch is that the work has to be completed by December 31, 2018. Visit for more details. Equipment manufacturers and natural gas suppliers often also offer rebates. A reputable HVAC technician will be able to tell you the offers available in your area.


An annual service inspection will ensure your furnace is operating at peak efficiency. But between visits from the pros, homeowners should replace the furnace filter at least as often as the manufacturer suggests. A clogged filter reduces airflow and causes the furnace to overwork. Homeowners with pets may need to be even more vigilant.

CAPTION: Photography courtesy of Margaret Mulligan

Jim Caruk, Renovation Editor

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