25 Different Types of Furnaces

There are many different types of furnaces available to keep your homes warm and cozy. Read on to find which one suits your home.
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Furnace in the living room.

Furnaces have a long history of heating homes which dates back to the Roman period, circa 1200 B.C. They used a type of warm-air heating system known as “hypocaust.” But after the fall of the Roman empire, people forgot about furnaces for about 1,000 years and used fireplaces instead. It was during the 13th century when Cisterian monks began using furnaces again to warm their monasteries.

Nowadays, a vast majority of homes in the U.S. and Canada are heated by furnaces. The most popular energy source is natural gas because it’s 30 percent more economical than electricity. Other energy sources are gas and oil.

Category

Natural Draft

Natural draft furnace

Source: Home Depot

This a very old type of furnace that typically had very few controls and was a simple design. Any heat created by this furnace would vent through chimneys made of masonry or brick and the circulation of air was dependent on pipes that were pitched upward. These pipes would help to channel the warm around through the floor and into the home and this worked because warm air rises. This very simple system didn’t have very many controls and was dependent on the type of fuel that you added and how well it burned to create any heat. Without a blower, it was impossible to force the air into the home. Any fuel that left behind solids had to be cleaned out before the furnace could be used again. Later, homeowners would adapt this furnace by using electric blowers to help to push the hot air out of the furnace and up and into the home. Wood and coal furnaces were controlled by how much fuel was in the furnace as well as how open or closed a damper was on the furnace while oil and gas systems relied on a thermostat to control the amount of heat produced.

Forced Air

Forced air furnace

Source: Home Depot

This type of furnace became popular in the 1950s as well as the 1960s and while it was a little more efficient than the natural draft furnace, the annual fuel utilization efficiency of these furnaces was nowhere near what it is today. They were incredibly bulky and were traditionally made with steel exteriors to help told in the heat. They could often be installed on the same pipe system as the natural draft furnace but had blowers that moved the heat through the home. These blowers were connected to belts and could operate at various speeds so that the homeowner had as much control over the heat in the home as possible. Over time, this furnace was adapted to work with air conditioning systems but at first, it relied on brick or masonry chimneys.

Forced Draft

Forced draft furnace

Source: Home Depot

An even more efficient type of furnace, the forced draft furnace had a multi-speed blower and a steel heat exchanger. They were a lot smaller than older furnaces, which made it much easier for the average homeowner to fit one of them into the house. They had combustion air blowers to pull the air through the furnace’s heat exchanger, increasing fuel efficiency while at the same time decreasing the necessary size of the heat exchangers. This hot air was then pumped up into the home to heat it. The multi-speed blower made it really easy for homeowners to adjust the amount of heat being pumped into the home and it could even connect to air-conditioning systems for the best possible climate control yet.

Condensing

Condensing furnace

Source: Home Depot

These are very high-efficiency furnaces that have a combustion area, draft inducer, and even a secondary heat exchanger. The heat exchanger is able to remove most of the heat that is released in the exhaust gas and condenses the water vapor and other chemicals while in operation. This means that the pipes have to strong enough to stand up to the mild acid created by these chemicals and are usually made of PVC instead of traditional metal. The draft inducer on this furnace makes it easy for the piping to be either horizontal or vertical, allowing for a number of different arrangements of this furnace. To have the most efficient arrangement possible, you will want to bring fresh air into the furnace from outside of the home. The combustion air produced is generally sent back outside the home with PVC piping in the same location as where fresh air is brought in.

Type

Single-Stage

Single stage furnace

Source: Home Depot

This type of furnace only allows gas to flow into the furnace at a high rate. They have a single gas valve that will open and close to allow gas flow. Since there is only a choice of “open” or “closed,” this means that a single-stage furnace is always either off or on. These furnaces are generally very noisy, only run at one speed, and continually pump out hot air as fast as they can. They are a great choice if you live in a fairly moderate or mild area as they work at 80% annual fuel utilization efficiency, which will keep you warm but won’t offer a lot of savings each month. In addition, this type of furnace is generally very inexpensive to have installed in the home as there is not a lot of technology that will increase the price of the furnace.

Two-Stage

Two-stage furnace

Source: Home Depot

When you opt for a two-stage furnace, you will have a little more control over the flow of gas as you can choose between high (full power) and low (half power). By communicating with the thermostat in the home, this type of furnace is able to adjust according to the heating load of the home. They operate at around 90% annual fuel utilization efficiency, which is an improvement over the single-stage furnace. By starting the furnace at half power, you can allow your furnace to operate and to heat up your home on cooler days. When your home starts getting colder because of the weather, then your thermostat will trigger the furnace to open up the valve and allow full power. This type of furnace also has an extended heating cycle when compared to the single-stage furnace. This means that the hot air will be better distributed and the home will be much more comfortable.

Modulating

Modulating furnace


Source: Home Depot

A modulating furnace runs at optimal heating all of the time by adjusting how much heat is released into the home. While models will vary, most operate with 1% increases or decreases, allowing the furnace to not only monitor how much heat it needs to release but carefully adjust its output by taking the temperature of the home into consideration. This means that this type of furnace is not only incredibly efficient but also provides very even temperatures throughout the home. It’s best used in homes where the winters are very long and cold and there is a high demand for heat for an extended period of time. This allows homeowners to take advantage of this pricier system. Since these furnaces are only running when it is necessary for them to be heating, they are great for helping cut down the monthly energy bills that you have.

Fuel Type

Electric

Electric furnace

Source: Home Depot

Electric furnaces are a great choice for many homeowners and one of the reasons is that they do not require a gas line. While some areas have natural gas available, there are many people who are unable to get this fuel source piped to their homes. Even if you do have natural gas in the area, it can be very expensive to have someone come and run the pipework for you, which will add to the cost of having a natural gas furnace installed. Most people have access to electricity, which means that they will easily be able to heat their homes with this type of furnace. Additionally, these furnaces are generally less expensive than other types, making them a great choice for families who are on tighter budgets or who are concerned about how they will finance their new furnaces. While there is always the chance that there will be an accident with an electric furnace, this is much less likely than with other types. There are no toxic fumes or carbon monoxide leaks for you to worry about with an electric furnace. Additionally, newer electric furnaces are much more efficient than they used to be in the past.

Natural Gas

Natural gas furnace

Source: Houzz

Furnaces that use natural gas as the fuel to heat your home have a number of benefits. In general, this type of furnace is fairly inexpensive to maintain because they do not break down very often; even when they do, they are relatively inexpensive to repair. This means that you don’t have to spend a lot to make any necessary repairs or to even replace the furnace when the time comes. Since natural gas is the least expensive of all fossil fuels that you can buy, running a furnace that uses natural gas will greatly cut down your monthly bills. Additionally, natural gas is the cleanest fuel to burn so you won’t have to worry about the pollution that you are creating each time you turn on your furnace to heat up your home. As well as being inexpensive, natural gas is also very efficient. This type of fuel will actually produce the most heat when it is burned, which allows you to use a smaller amount when heating your home. As reliable as natural gas furnaces are, homeowners do not have to deal with breakdowns very often and when they do, they are relatively easy and inexpensive to repair.

Oil

Oil furnace

Source: Home Depot

Oil furnaces are a great choice if you have space on your property where you can store the oil for when you need it and are willing to work with a delivery company to have them come and fill up your tank on a regular basis. If you forget and run out of oil, then you will not be able to heat your home until the company comes back and is able to refill your tank. Oil furnaces provide a lot of heat and actually produce more per BTUs than other types of furnaces. While maintenance is fairly easy for this type of furnace and the oil delivery company is usually happy to provide homeowners with this service, it does cost more due to the soot and dirt buildup that occurs. If the oil filters aren’t changed on a regular basis and the chimney isn’t cleaned, then you and your family will be at risk of a fire. These furnaces generally cost less than gas furnaces but the fuel costs more and they are less efficient so it’s important for homeowners to weigh immediate savings over savings in the long term.

Propane

Condensing furnace


Source: Home Depot

More and more people are opting for propane furnaces because this type of fuel can be used almost anywhere and doesn’t require gas lines. By connecting a furnace to a large propane storage tank, the family is able to heat the home with little hassle. Just as with an oil furnace, however, if the propane in the tank runs out, then there is not any way to heat the home so the tank needs to be filled on a regular basis so the family will stay warm. Propane furnaces are very adaptable and can even be adjusted to burn natural gas instead of propane if there is a propane shortage or the prices increase so much that it is not affordable as a fuel option anymore. Since propane burns so hot and is actually hotter than other fuels, it can heat up a home very quickly and produce incredibly hot air that will allow the homeowner to set the thermostat very high. These furnaces generally last for around 20 years. Unfortunately, as easily obtained as propane is, prices are increasing and it is more expensive than other fuel options. Propane furnaces do not produce as many emissions as using electricity to heat the home but these furnaces do need to be checked on a yearly basis for leaks and other problems to ensure that the furnace is working correctly and meets all safety standards.

Wood

Wood furnace

Source: Hayneedle

Wood furnaces are very reliable, dependable, and efficient and fill the gap for people who can’t afford or do not want a different kind of furnace at their homes. Being able to eliminate a lot of the monthly heating bills that you have by relying on wood as the fuel source for your furnace is a great relief for a lot of people. Many people are now opting for wood furnaces and then moving them outside where they can be set up to heat a number of different buildings all at once. This will reduce the risk of a fire, which is one of the main reasons why homeowners shy away from using wood furnaces. A higher-end wood furnace that is maintained on a yearly basis can last indefinitely while not having your furnace cleaned out and opting for a lower-quality model will greatly shorter its lifespan to just around a decade. One of the most important things that homeowners can do to keep their furnaces working correctly for as long as possible is to keep them free of creosote and rust. While fuel prices seem as though they are always increasing, as long as you have a source for wood at your property, you won’t have to worry about the cost of fuel for your wood furnace going up. This is ideal for people who live on a large area of land and are able to harvest and cure their own wood as it greatly decreases their dependency on fuel companies. Some people think of wood furnaces as being fairly dirty and while they do emit smoke that is dangerous to breathe for long periods of time, a great exhaust system that has been professionally installed will help to lower the risk of smoke inhalation.

Coal

Wood furnace

Source: Wayfair

In the same way that wood furnaces have a number of fans who appreciate how they cut the user’s dependence on outside companies and allow for great heating, people who have coal furnaces experience a number of the same benefits. These furnaces generally have very few moving parts, which means that they are much less likely to break down or to require expensive repairs. Modern furnaces produce the high heat that coal is so famous and popular for releasing without also allowing the dangerous soot and smoke to enter a home. Using anthracite coal that is widely available allows the homeowner to heat without fear of any smell. This type of coal is almost 100% carbon and is used to heat, unlike the other common type of coal, bituminous, which is used to create energy inside power plants. Using the right kind of coal will ensure that you do not have billows of black smoke in your home and will decrease the chance that anyone can even tell that you are using coal as your fuel source. Of course, there is some dust as well as ash when cleaning out the furnace but, in general, this fuel source is very easy to manage and does a great job heating up the entire home.

BTU/Hour

Low

Furnace with low BTU/hour

Source: Home Depot

Furnaces that have lower BTU ratings will generally be a little less expensive than ones that have higher BTU ratings but opting for this furnace as a way to save money when heating your home can backfire on you if you are not careful. Homeowners who have very large or drafty homes will end up paying more money to heat their homes each month with a furnace with a low BTU rating because the furnace will turn off and on regularly instead of providing consistent heating in your home.

Medium

Furnace with medium BTU

Source: Home Depot

While a medium BTU rating may not seem to be the best option as people are conditioned to believe that higher is better, this may be the right choice for you depending on your home, how large it is, what kind of insulation you have, and even the average temperature of the area where you live. This is why it’s a good idea to have an expert come and help you choose the right furnace so that you don’t overpay for one with a higher BTU rating and not get much of an additional benefit.

High


Furnace with high BTU

Source: Home Depot

While homeowners tend to assume that furnaces with high BTU ratings will produce the most heat possible, it’s important that this high rating coincides with a high efficiency so that your home will heat quickly and without frustration. By choosing a furnace that has a BTU rating that is too high, homeowners will often have to deal with furnaces that are running more than necessary. This means that it will have trouble keeping your home warm during the coldest days of winter and will greatly increase your heating bills.

Features

Energy Star Rated

Condensing furnace

Source: Home Depot

Furnaces that have been Energy Star rated have been selected by a program operated by the U.S. Department of Energy and the U.S. Environmental Protection Agency as being very efficient and great at saving energy. These typically will use 20% to 30% less energy than what is required by the mandates from the government. They have to have an annual fuel utilization efficiency of more than 90% to be Energy Star rated.

Smart Technology

Natural draft furnace

Source: Home Depot

If you want to make sure that your furnace is operating the best that it possibly can, then you will want to opt for a furnace that comes complete with smart technology. When shopping for a smart furnace, you will need to pay attention to the various features as not all will have the same. This means that your furnace may have intelligent controls that can remind you when it is time to change the filter, adjust the zones in your home automatically, and even monitor your airflow. Additionally, this feature will keep an eye on the temperature inside and outside of your home and make it possible for you to monitor your furnace when you aren’t at home by using your computer, smartphone, or tablet. Obviously, these furnaces are going to cost more but many people find the additional features worth the increased price.

Buy it on Home Depot here: https://www.homedepot.com/p/Kelvinator-95-AFUE-80-000-BTU-2-Stage-Upflow-Horizontal-Residential-Natural-Gas-Furnace-KG7TC080D-35C/206511956

Sealed Combustion

Furnace with medium BTU

Source: Home Depot

This will not only protect your home from the risk of carbon monoxide but is much more energy efficient. Sealed combustion furnaces will maintain more of the heat that they create so that your home is efficiently heated.

Buy it on Home Depot here: https://www.homedepot.com/p/Winchester-100-000-BTU-96-2-Stage-Variable-Speed-Multi-Positional-Gas-Furnace-W9V100-421/202771093

Air Flow

Upflow
Furnace with medium BTU

Source: Home Depot

These furnaces draw cool air into the furnace through the base or the top. They then will push warm air through the top of the furnace and are a great choice when the ductwork will be above the furnace.

Downflow


Condensing furnace

Source: Home Depot

By taking cool air from the top and then releasing warm air from the bottom of these furnaces, they are great when the ductwork is below the furnace.

Horizontal

Single stage furnace

Source: Home Depot

These furnaces lie on their sides, bringing in cool air from one side and releasing it from the other. They don’t need a lot of vertical space and are great in attics or basements.

Upflow/Horizontal

Single stage furnace

Source: Home Depot

These furnaces can be used as a left or right horizontal or upflow furnace.

Downflow/Horizontal

Furnace with downflow/horizontal air flow

 

Source: Home Depot

These furnaces can be used as a horizontal (right or left) or downflow furnace.

 

Multiposition

Single stage furnace

Source: Home Depot

This type of furnace can be installed in horizontal left, horizontal right, upflow, or downflow positions.

 







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