How do we keep our buildings warm when it’s cold outside? The answer to this question can be both deceptively simple and astonishingly complex. The reality is there’s no “one size fits all” answer to such a question, just as with air conditioners. Whether you’re thinking about your home or your responsibilities involve proper facilities management for a commercial building, understand the various heating options on the market is important. Not only will such information help you to better understand the systems you have in place, but it can enable you to make smarter choices in the future when comparison shopping for a new installation.
To help develop your understanding, consider the following fifteen examples of some of the main types and styles of home and commercial furnaces in use today. First, we’ll consider the fuel each type of furnace use. Then we’ll examine other differentiating factors.
Type of Furnace by Fuel
- Wood furnace: A very traditional type of furnace, wood-burning stoves and furnaces are not very common today. Burning wood to heat air generates a substantial amount of pollution, and even efficient wood-burning stoves can typically only heat small to medium size spaces.
- Natural gas furnaces: Though fewer homes have access to natural gas lines, gas-fired furnaces are a popular option in the commercial space. Highly efficient and relatively clean-burning, furnaces that burn gas are excellent for situations that demand fast, reliable heat.
- Propane furnaces: An uncommon installation, propane furnaces connect to an on-site tank, making it a good option for remote homes and sites away from the traditional utility grid. Operating costs are typically higher due to the cost of propane fuel. However, for rapid heating or heavy duty usage, they’re a good choice.
- Petroleum furnaces: Oil-burning furnaces are especially common in states with longer winters and in commercial applications owing to the huge amount of heat they can produce. These require on-site fuel storage, rather than a utility connection, which can pose logistical issues. Fuel prices can also vary widely.
- Electric furnaces: A good all-around option for homeowners, electric furnaces don’t work well in commercial applications due to the need for more heating power. Electricity is used to heat special coils, over which air blows before entering the household. These are often found in combination with a typical air conditioner.
- Hot Water/Steam: Boiler systems use the heat from steam or hot water to warm spaces by circulating through special pipes or radiators. Fuel oil or natural gas must be burned to heat the water. However, boiler systems are a class all their own compared to other furnaces that use the heat from burning fuel to warm the air.
- Renewable Energy (Solar or Geothermal): A type of electric furnace, some heaters rely on deep geothermal power (as some new construction offices do) or through the usage of solar panels. Most renewable-powered buildings have a backup furnace of a more typical type, such as a boiler or an oil furnace.
- Non-fuel burning (heat pump)
Heat pumps, or “reverse air conditioners,” use electricity to circulate a refrigerant that exchanges heat between the outdoor environment and the indoor space. Heat pumps are often combined with air conditioners as a matter of design. They burn no fuel and do not “create” hot air in the same way as a typical furnace. Some heat pumps may tap into geothermal heat found underground.
By Circulation Type
- Condensing: Highly efficient, condensing furnaces are so-named because the exhaust gas is cooled so thoroughly by a heat exchanger that it condenses to a liquid. By using a secondary heat exchanger, heat what would be typically wasted is instead brought back into the system.
- Natural Draft: Uncommon today, natural draft uses the normal rising motion of hot air to bring it upward into a dwelling. Some use electric fans to help move the air into spaces that would otherwise be difficult to reach.
- Forced Draft: A more modern design, forced draft furnaces use a single heat exchanger to achieve more thorough heating of the air before using electric blowers to send the air through duct work. The name comes from forcing air into the combustion chamber for better efficiency.
- Forced Air: This refers to any furnace that uses fans to force air through duct work and bring heat into the home. Electric furnaces, for example, are often forced air units. This catch-all term can be used to describe many kinds of furnaces.
By Combustion Type
- Modulated: A very efficient modern type of furnace, those with modulating fuel control can provide very small increments of heating power. Instead of running and then shutting off in a continuous cycle, modulating furnaces often run as long as the thermostat is set to provide heat.
- Single stage: Single-stage furnaces feature no fine control options for the flow of fuel into the combustion chamber; it is either on or off. Most furnaces today in homes are single-stage, providing a continuous flow of hot air at the thermostat-set temperature.
- Dual stage: Two-stage furnaces can partially open the fuel valve, allowing for a reduced power setting. This occurs automatically to provide more continuous, even heating at a higher efficiency. Special programming allows two-stage furnaces to detect how best to use these settings.
Which is the right choice?
Furnaces can come in a wide variety of combinations considering all the many different types listed above. Not only will you face decisions about each type of furnace out there, but you must also consider individual unit efficiency ratings, cost-effectiveness, and more. Navigating this process can be intimidating, but with professional assistance, selecting the ideal heating system for a given application is much simpler. Whether you have questions or need to secure a better heating system before the next winter season arrives, consider reaching out to a respected furnace installer in your area for help.