The common home heating solution

Furnaces can be powered by fuels like oil, natural gas or propane, or with electricity. The most common types found in residential homes are electric and natural gas furnaces.

Natural gas furnaces generate heat by burning fuel. The hot gas resulting from this combustion passes into heat exchangers (curved metal tubes), which transfer the heat to air flowing through the home's air ducts and into the home. Gas furnaces create carbon monoxide, a colorless and odorless gas, that's released outside through a vent or pipe. Carbon monoxide poisoning occurs when a crack or leak forms in your gas furnace, allowing CO into your home. This is why installing carbon monoxide detectors within the home and having your furnace serviced annually are so important.

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Electric furnaces are both cleaner and safer than gas furnaces. However, they are also twice as expensive to run. Electric furnaces use electricity to create heat with wire coils. Air is forced into a heat exchanger via an air fan and enters the home through a duct system.

Furnace Filters

Your furnace filter is key to the efficient operation of your furnace and the air quality in your home. Although some furnace filters are very inexpensive, many of them will only catch about 75 percent of bulk dirt and 3 percent of minute pollutants.

Treated furnace filters are generally more effective. These disposable furnace filters are treated with dirt-trapping glycol or mineral oil. They may only capture about the same amount of bulk dirt, but they can catch about 10 percent of the smaller, microscopic particles. Most disposable filters are made of fiberglass or carbon and cost less than $10 online. You should replace your furnace filter every month, or as needed, to cut down on heating bills.

Electronic furnace filters or electrostatic air filters are the most effective. Some brands claim to remove up to 97 percent of large particles and 70 percent of microscopic particles. Most permanent furnace filters range in price from about $60 to $400 online for a complete unit. These can often last for years, but need regular cleaning to stay effective.


Your home's heating and cooling systems are controlled by a small piece of equipment called a thermostat. Today, most homes have a digital thermostat with a programming option.


Digital thermostats are preferred over mechanical thermostats because they can be programmed to raise or lower the temperature automatically at set times of the day. This way, for example, you can avoid heating the house when no one is home during the day. Digital thermostats measure temperature by means of a thermistor. This is an electrical resistor whose resistance change depending on temperature. A microcontroller measures the resistance in the thermistor and converts it to a temperature reading. The thermostat turns the furnace on or off based on this reading, to maintain the temperature you have programmed.

Your thermostat should be located in a room that is used frequently. In order to read your thermostat easily, it should be installed at eye level. It should also never be placed on an outside wall, near a window or be exposed to direct sunlight or other heat-conducting appliances.

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