Heating your home seems as simple as adjusting the thermostat and enjoying the results. Of course, it’s not nearly that simple, and your furnace works hard just out of sight to keep your home comfortable. But as it works hard, it may be drawing closer to retirement, which means a replacement may be in order. Replacing your furnace, too, is more complicated than it may first seem, with a variety of models that work in different ways. Here’s a field guide to some of the many different types of furnaces.
Furnaces by Fuel Types
Most furnaces in the United States and Canada run on natural gas supplied from underground pipelines. However, there are some exceptions. In Québec, which enjoys a surplus of hydroelectricity, many homes rely on electric heating options, whether from furnaces or baseboards. In parts of New England and the Canadian Maritimes where it’s difficult to lay gas lines, furnaces often run on heating oil from exterior fuel tanks. In the American Southeast, where winters are mild and demand for home heating is lower, many homes employ electric heat pump systems. In highly remote regions, some homes even burn wood as their primary source of heat. Consider your energy costs and utility options.
Furnaces by Efficiency
Whereas most furnaces convert about 80 percent of their fuel into heat, with the remainder discharged as exhaust, high-efficiency models use a secondary heat exchanger to draw additional heat from the exhaust, turning as much as 97 percent of their fuel into heat. A new furnace is likely to be a high-efficiency model. While increased efficiency means lower fuel costs, these models do come with drawbacks. Secondary heat exchangers are prone to water leakage, and high-efficiency furnaces work hard and wear out more quickly. If a high-efficiency furnace fails after 15 to 20 years, it’s likely to need an outright replacement instead of repair, and both times, you’ll pay more upfront for your lower heating bills.
Furnaces by Heating Stages
Another way to categorize furnaces is by how many stages of heating it uses: one, two, or variable. A single-stage furnace is simple—it’s either on or off. When it’s on, it works hard to get your home to the desired temperature, and then, when it’s finished its work, it shuts off. This type is simple but inefficient since starting back up again is hard work for the furnace, and those chilly lulls between ideal temperatures can be uncomfortable. A two-stage furnace has a high and low heat output and can toggle between the two, preventing erratic temperature shifts by using sustained and consistent heat from a lower output. However, these consistent temperatures come at the expense of higher energy bills. Variable-speed furnaces regulate the motor of the furnace’s blower, heating the home with increased accuracy and efficiency. Among the different types of furnaces, variable-speed furnaces lean the heaviest on their air filters because they run the most often. Though you will more regularly change your 20x30x1 AC filter, you’ll enjoy the cleanest possible air in your home.
