Buying a New Furnace? From Important Terms to Supplemental Equipment

Published on: January 30, 2014

Whether you’re seeking a new furnace to improve your home comfort or to save energy and money long term, it pays to be an educated consumer. Most people realize that new furnaces with the blue Energy Star label help you to make a wise choice. When you look for this label on a new gas furnace for your home here in the Southeast U.S., you’ll typically save 12 percent or more on your energy bill over standard gas furnaces.

Energy Star labeled furnaces have higher AFUE efficiency ratings and highly efficient blower motors. You’ll also see a distinct label this year that states “Most Efficient,” designating the top performers. To save money long-term, plan to pay a bit more upfront to get the highest efficiency model you can, and choose your furnace from the highest-efficiency category—89 to 97 percent efficient condensing furnaces. Read on for key furnace terms and tips on selecting supplemental furnace equipment, as well as safety and efficiency features to help you get the best furnace for your home.

Common Furnace Terms You Should Know

  • Annual fuel utilization efficiency, or AFUE: This efficiency rating is an important indicator. The higher the AFUE, the more efficient the unit.
  • Chimney liner: A code-compliant metal pipe or tube that goes inside the chimney to protect masonry and ensure safety and efficiency.
  • Condensate: Not surprisingly, this substance—a mix of combustion by-products and water—is formed by condensing furnaces.
  • Condensing furnace: These units have an AFUE of 89 percent or above. Greater efficiency comes from extracting heat from the exhaust, condensing out the water.
  • Dehumidifier/humidifier: This equipment, which removes or adds moisture to the home’s air supply, can be integrated into your central AC and heating system.
  • Ducts: These are large conduits within your walls, under floors and in crawl spaces that circulate conditioned air throughout your home. Supply ducts distribute heated air from furnace equipment to the house. Return ducts bring the cooled-off air back to the furnace to be reheated. Ducts should be sealed to prevent energy loss, especially those in unconditioned spaces of your home like crawl spaces. Your local HVAC professional can inspect and seal your ducts.
  • Energy loss or heat loss: The rate of heat loss is measured in British thermal units (BTUs) per hour. The contractor should calculate the heat loss for the coldest weather expected to help choose the right capacity heating system for your home.
  • Forced air heating: This heating system uses a blower to circulate the heated air through the home.
  • Heat exchanger: This furnace component transfers heat from burners to the air circulating through the system.
  • Power venting: This system uses a small fan to blow exhaust to the outside of the home, which generally penetrates the side of the home.
  • Sealed combustion: With this heating system, combustion air for the furnace burners comes from the outdoors.
  • Setback: This refers to turning the thermostat down to reduce costs during away-from-home and sleeping hours. Use a programmable thermostat, which will automatically take care of setbacks.
  • Vent: The wall opening that exhausts furnace gases outdoors.

Properly Sizing Your New Furnace

Your furnace should be sized to match the heating needs for your home. Your HVAC professional can determine the ideal capacity by load calculations for your home. An experienced contractor doesn’t size a furnace based only on the home’s square footage. Many factors come into play and should be considered, including your unique insulation levels, window types and area, and airtightness.

While oversizing a condensing furnace won’t drastically increase your energy costs, it can interfere with your future home comfort, causing uncomfortable temperature swings and blasts of airflow out of the registers. Undersizing a furnace is less likely to happen, since contractors would rather err on the side of slightly too much heating capacity, rather than too little. Once the furnace has been selected and sized, your HVAC contractor should make sure the duct system is adequate and integrates well with your furnace and supplemental furnace equipment.

Supplemental Furnace Equipment and Features to Increase Efficiency

  • Chimney liners are often called for by the heating system manufacturer as supplemental furnace equipment if your new furnace is in the 80 percent efficiency range. Don’t vent a new furnace with plastic piping through an unlined chimney counter to manufacturer requirements. If a liner is required for your gas water heater only, compare the cost of replacing your water heater with a power-vented model with the cost of the chimney lining and installation.
  • Filters or integrated/electronic air cleaning equipment help extend the life of your new furnace and reduce repairs. These are essential pieces of supplemental furnace equipment. Choose 1-inch or 2-inch pleated filters compatible with your air cleaning system for better dust removal without airflow restriction. Duct modifications may be needed as part of the furnace installation. Ask for an external filter slot with cover to help keep your ductwork sealed.
  • Programmable thermostats don’t really count as supplemental furnace equipment anymore. They should be integral to your system. Programmable thermostats allow you to save energy with automatic adjustments while keeping you comfortable when you’re at home and awake.
  • Sealed combustion design offers safety, which is just as important as saving the planet and saving money on operating costs. This system is designed to use outdoor air for combustion and is equipped with an air-intake pipe and exhaust pipe. Choose a safer sealed system to help avoid furnace corrosion from laundry vapors mixing with indoor combustion air, using up/wasting the indoor air that you’ve already heated and backdraft danger, where exhaust is pulled down into the home via the chimney.
  • Variable-speed furnaces, also known as two-stage furnaces or multistage heating systems, allow low speed fan operation and low burner output. This saves energy and money because the system only runs on high when truly needed—on the coldest days, at the coldest times. Variable speeds also mean quieter operation, slower airflow from room air registers and more consistent/accurate temperature control. For further savings, multi-speed furnace fans use efficient motors (ECMs or electronically commutated motors or brushless DC direct current motors) to save electricity. Verify that the variable-speed furnace you’re purchasing has one of these energy-saving motors and check that they’re covered under the warranty.
  • Zoning systems allow you to enjoy different temperatures in different rooms (zones) of the home, or leave unused areas unheated to save energy. Zoned heating and cooling systems are controlled by individual thermostats or sensors.

Features of a New Furnace

If you’re upgrading the furnace in your home for the first time in decades, there are several features that may be new to you:

  • You won’t have a continuously burning pilot light.
  • Your new heating system will have more safety controls.
  • You may feel stronger airflow from your room heating registers at lower temperatures than with your old system and the new furnace blower may run longer.
  • You’ll see a plastic drain hose running from the bottom area of your condensing furnace to a drain. Plastic exhaust pipe vents will run horizontally through a wall of your home or up through the roof. Keep the vent piping and drain hose unblocked and free of obstructions for optimal furnace operation.

How Much Will Your New Condensing Furnace Save?

Old furnaces are often rated with AFUEs around 60, which means, if you still have one, it’s wasting 40 percent of every heating dollar. Switching to a condensing furnace with an AFUE of 90 should save you about 30 percent on your home heating costs.

Need guidance in choosing your new furnace or supplemental furnace equipment? Visit us at AC Southeast® for more valuable HVAC advice and to find a quality HVAC contractor in your neighborhood.