Forced-air furnaces

A forced-air natural gas furnace uses ductwork and vents to distribute warm air throughout the house. The primary components of this system include an air filter, blower, heat exchanger and various controls. A thermostat is used to control the temperature in the house.

ENERGY STAR® certified systems

If your furnace was installed before 1990, it’s likely a lower-efficiency model, averaging between 60 and 70 per cent AFUE. Consider upgrading it to ENERGY STAR®. ENERGY STAR certified natural gas furnaces in Canada are rated between 95 to 99 per cent AFUE. This means when the furnace is installed to a quality standard, you only lose one to five per cent of the heat, approximately.


Comfortable, evenly balanced warmth: forced-air heating usually brings in fresh air from the outside for ventilation, creating a healthier environment than electrical baseboard installations, which have no ventilation component.

Improved air quality: the furnace’s air filter reduces airborne pollutants such as dust and improves indoor air quality. The sealed combustion in high-efficiency models also protects indoor air quality by isolating the burner and flue from the home.

Furnace efficiency

Look at the furnace’s Annual Fuel Utilization Efficiency (AFUE), a rating system used to estimate the equipment’s efficiency. The higher the rating, the more efficient the furnace is.

Understanding furnace efficiency

Upgrading your furnace can improve your home's energy efficiency and save you money on heating costs.

Many homes may still have mid-efficiency furnaces (78 - 82 per cent).   These mid-efficiency furnaces are no longer available for purchase in the province if the manufacturer date is listed after January 1, 2010.

High-efficiency (condensing) furnaces (95 - 99 per cent) are now mandated for new construction and for furnace replacement in existing homes, giving you up to 99 cents worth of usable heat for every dollar you spend.  Standard-efficiency furnaces that are 20 years old or more may be as little as 60 per cent efficient, while post-1990 mid-efficient models can achieve an annual efficiency of 78 to 82 per cent.

Furnace buying tips

Buying a new furnace is a major purchase. It’s not a decision you want to make hastily on a cold Sunday in January. A little research will go a long way to help you find the furnace and contractor best suited for the job.

Ensure a quality installation

Just as important as the furnace itself is the quality of its installation. In BC there are codes to follow for the venting and gas fitting, but there are no standards for the actual installation of the furnace itself. Here are some steps to help ensure your new furnace is installed properly.


Choosing a contractor

Always use a natural gas contractor who is licensed with Technical Safety BC and employs certified gas fitters. They should also be bonded and insured, offer you a warranty and provide references and follow-up service.

You can find contractors meeting these criteria through our Trade Ally Network directory. As an extra step, check to see if the contractor is in good standing with the Better Business Bureau.

Get quotes

We recommend you get three quotes before deciding who will do the work. Ask each contractor to inspect your existing system. Each should provide you with a detailed quote listing all of the work to be performed, as well as the cost. Remember, the best price is not always the best deal. A low price could be an indication the contractor may take shortcuts.

What to discuss during the quote consultation

  • Ask the gas contractor to perform a heat loss calculation to confirm what size furnace your home needs. You don’t want to pay extra for an oversized system providing more heat than your home needs.
  • Let the contractor know if there are any cold spots in your home. 
  • The contractor should inspect your existing ductwork to ensure it’s sized properly for adequate airflow and air return with the new high-efficiency furnace that will be installed. 
  • Tell your contractor you’ll require an installation permit. This permit, from Technical Safety BC, or licensing organization in your jurisdiction, helps to ensure gas installation code compliance and makes sure the installation is registered with the safety system. Plus, if furnace rebates are available, only permitted installations will be eligible. 
  • Ask the contractor for details about the warranty.

During installation

These extra steps during installation will help maintain furnace longevity and help it run as efficiently as possible. Hint: a good contractor will have provided details of this work on the quote.

Tapered transitions: tapering these transitions between the plenum and the top of the return and supply air ducts can help reduce noise and electricity consumption of the furnace’s fan motor.

Two pipes are better than one: high-efficiency furnaces can be vented directly through an exterior wall, instead of the chimney. The venting should be double-piped, one pipe for fresh air intake and the other for exhaust. Both pipes should be vented to the outside together.  A properly sized two-pipe system helps with overall energy efficiency for the home, is quieter and reduces the chance of maintenance and combustion issues.

Pleated two to four inch filter: ask if your ductwork can be modified to fit a two to four inch pleated filter. Pleated filters improve air quality, as they are more effective than fiberglass or reusable types at filtering particulates. And thicker pleated filters have more surface area than one-inch types. This results in quieter operation, furnace longevity and electrical energy savings. Turning vanes, just upstream of the filter, also help to introduce the return air to the entire filter.

Matching or compatible thermostat: to achieve the full system performance of your new furnace and to maximize the overall comfort of your home, ask for a furnace compatible (or matching) thermostat. These mini-microprocessors allow for quick recovery and can offer more precise, even heating.

Sealed joints: have the contractor seal the joints on the exposed ducting with approved foil tape or paint-on duct sealant to prevent heat loss in the duct joints.

Tipped to drain: high-efficiency furnaces have double heat exchangers that extract heat from the combustion exhaust.  Once the heat is captured, the remaining condensate turns into acidic water. If not drained away from the furnace, a buildup inside the furnace could lead to premature equipment failure. Your contractor will install the furnace to ensure the condensation drains away from the furnace.

Furnace maintenance

Schedule regular inspection, cleaning, servicing and tuning-up of your natural gas furnace to ensure it operates safely, reliably, and at peak performance.

The owner’s manual is the best source of maintenance information and operating instructions. A licensed gas contractor should inspect and maintain your gas home heating system. When selecting a contractor, make sure to choose a licensed gas fitter who is experienced at inspecting and servicing your gas appliances for safe operation.

Important tips

  • Schedule maintenance for your furnace as early in the fall as possible, so it’s working as good as new when the cold weather sets in.
  • Change or clean filters at least once every three months and keep the fan compartment door tightly closed. Filters are located at or near the blower compartment of the furnace and are held in place by a clip. Filters are very important for maintaining healthy air quality.
  • If your furnace has a fan belt, inspect it for cracks or signs of wear (and replace if necessary) at the same time as you change the furnace filters.
  • Keep vents and air returns clear of obstructions like furniture, lint, dust or pet hair.
  • If your furnace motor has oiling points, apply one or two drops of SAE 20 non-detergent oil every heating season. Avoid over-oiling.
  • Keep the area around the furnace clear. Don’t store items against the furnace. Don’t store flammable items in the furnace room.

Tip – When inspecting or changing filters or fan belts, shut off the electricity at the furnace switch and at the circuit breaker panel first.

Furnace safety

Regular inspection and maintenance is the best way to keep your furnace working well. A qualified gas contractor should do an annual furnace inspection and service.

Warning signs

Stay alert for these warning signs that a furnace isn’t working properly:

  • frequent pilot light outages (only on older model furnaces)
  • delayed ignition (mid- and high-efficiency furnaces have an intentional delay. Check your manual)
  • a yellow or wavering flame
  • excessive soot or corrosion on the appliance or vent (white, brown or black streaks)
  • signs that the flame has “rolled-out” of the furnace, like scorch marks by the door or other opening
  • too much or too little heat
  • a continuous or intermittent odour, either the “rotten egg” or sulphur smell of natural gas or a sharp odour that causes eyes to sting
  • symptoms of carbon monoxide poisoning: nausea, headaches, lethargy or other flu-like symptoms

If your pilot light goes out

All natural gas appliances with pilot lights are designed to shut off automatically if the pilot goes out. To relight the pilot, follow the manufacturer's instructions (usually located on a metal plate near the furnace burner or gas controls). If it fails to relight, turn off the manual valve to the natural gas supplying the furnace and call a qualified gas contractor.