Furnace features and types

Here are some features and considerations experts say you should think about when choosing a gas or oil furnace, assuming that the contractor has determined the correct size for your house.

  • High-efficiency or 80 percent efficient? If you live in an area with harsh winters, you should recoup the additional expense of a high-efficiency condensing furnace (90 percent AFUE or more) over the unit's lifetime. However, if your winters are more temperate, you may be better off with an 80 percent model. If you're unsure, have your contractor calculate fuel costs for both kinds of furnace, using your current bills; then you can tell if future fuel savings justify the additional $1,000 or more for a 90 percent furnace.
  • Repair or replace? According to the 2008 Consumer Reports Buying Guide, an annual volume published by the editors of ConsumerReports.org, "increased efficiency is not usually an economically valid reason" to replace an old furnace that is still in good working order. Experts generally recommend replacing your old furnace if any of the following apply: it's more than 15 to 20 years old; it has a pilot light rather than electronic or hot-surface ignition; it does not have vent dampers or a draft fan; it is a coal-burning model that has been converted to gas or oil.
  • Improve your home's efficiency. Before you invest in a new heating system, experts advise improving the overall energy efficiency of your home through steps like adding insulation and sealing air leaks. This will reduce the heating load of your home, allowing you to purchase a smaller furnace.
  • Variable-speed blowers improve the efficiency of your heating system. This device allows the furnace to run at high speed in colder weather or low speed in milder weather. This feature not only saves energy but also reduces wear and tear, because the furnace isn't always cycling on and off. Furnaces with variable-speed blowers produce fewer drafts, maintain a more constant temperature and make less noise, because they're not always running on high.
  • A programmable thermostat will save energy by reducing the amount of work your furnace must do when no one's at home. For each degree you turn down the thermostat during an eight-hour period, you can reduce your heating bill by about 2 percent. Programmable thermostats can keep the house at a lower temperature when you're not home or at night. Replacing the old thermostat is a job most homeowners can do themselves, according to the Department of Energy.

Experts stress the importance of taking the time to find a good HVAC professional. If you do not know one, you can ask friends and neighbors for references. Ideally, you should get estimates in writing, along with customer references, from at least three contractors. Make sure the contractor does a thorough survey of your home to calculate the size of the system you will need. Your contractor should be licensed and insured, and the technician who installs the system should be certified by North American Technician Excellence (NATE).

Once your furnace has been installed, proper maintenance will keep it running at top efficiency. Steps to take include cleaning air registers, baseboards and radiators and cleaning or replacing air filters. Your heating system should also be tuned up periodically: once a year for oil-fired furnaces, once every two years for gas-powered models. Editors at ConsumerReports.org say that human error, such as inadequate maintenance (or improper installation) accounts for twice as many furnace problems as defective equipment.

Watch the video

To learn more about caring for your gas furnace, watch this About.com video on how to light a furnace pilot light.

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