As we enter into the cold months of the year, you are probably ready to crank that thermostat all the way up to keep you and your home warm. Heating bills are a major cost for some people in the country as they are often one of the most expensive home utilities.
Not all heating systems are equal, though, and some are more effective and more efficient than others. So we will cover the main types of heating systems, how they work, and how efficient they are.
Furnace (Forced Air)
Forced air heating systems are the most common type around the US. Most homes depend on a furnace to provide heat. The furnace blows heated air through ducts in the house to deliver heat to the various rooms in the house. Furnace systems are also sometimes called forced air or ducted warm-air distribution systems. These furnaces are powered by natural gas, fuel, electricity, or oil.
To get a little more specific, furnaces produce a flame that heats a component called a heat exchange. This heat is transferred into the air and then is pumped through a series of ducts out into the building. “Inducer” fans pull the gas out of the heat exchange to create a draft that circulates heat through the building. Many modern furnaces reclaim heated gas by cooling it until it condensates.
Most furnaces have a single thermostat system that will turn the furnace on when temperatures drop below a certain range. Furnace efficiency is measured by a metric called Annual Fuel Utilization Energy (AFUE). The higher the AFUE, the more efficient the furnace is.
Boilers systems heat homes through heating water. The boiler uses natural gas or some other fuel to heat water into steam. Then, this steam is piped through radiators and other ducts through the house to radiate heat. The excess heated water vapor then condenser onto a collector, which recycles the water to be heated again. These kinds of steam boilers are older and are less common nowadays.
A more common boiler heating method is hot water boilers. These boilers work much like steam boilers, except they do not produce steam, just hot water. Like steam boilers, hot water boilers typically use natural gas as fuel. Oil boilers do exist, but they are less common in the US because oil has a lower latent heat potential than natural gas.
Boilers use pumps instead of fans to circulate heated water. Boilers are usually more expensive to run than furnaces, but they are more capable of target “zone” heating, which can control temperatures in individual rooms.
Heat pumps are a relatively new heating system that uses pumps to extract and circulate heat. Heat pumps work by essentially cycling cold air for hot air. During the summers, heat pumps move hot air from the inside to the outside, and during winter, they move heat from outside to the inside of the house. Heat pumps tend to use a forced air distribution system, similar to that used by furnace heating systems.
There are two main types of heat pump systems: air-source and ground-source. Air-source systems take in heat from the outside air during the winter and use outside air as a heat sink during the summer. In contrast, ground-source systems channel heat from underground, where temperatures are usually more constant than the air. Ground-source systems are typically more efficient and better at maintaining a constant temperature, but air-source systems are more common and easier to install and setup.
Ground-source systems are more expensive because they require a significant amount of landscaping. A “loop’ must be installed in the ground in trenches 3’-6’ deep. Costs of installation can vary greatly depending on soil conditions, available space, and the particular installer’s experience. A handful of these systems use groundwater reservoirs for heat exchange rather than refrigerants.
Most heat pump systems use electricity to pump air but not to produce heat. This means that many heat pump systems can move more energy than they use. As such, heat pump systems are highly efficient and usually run at a relatively lower cost than other common house heating methods. However, they are unable to reach the high temperatures of some other heating systems.
Direct Heating Systems
Some homes use a direct heating system rather than a centralized system that heats through some other medium. Direct heating systems lack ductwork and directly generate heat in the surrounding area. As such, direct heating systems usually have a relatively low coverage area and are typically used from smaller homes or single rooms.
The most common kind of direct heating system used in homes is a space heater, which can be either gas-powered or electric. Gas-powered heaters tend to be permanent fixtures and are connected to the house’s gas mains. Gas space heaters combust gas to create heat, then funnel the combustion products out of the room, usually through a series of pipes installed in the walls. These kinds of heaters can use gas, oil, or kerosene as fuel.
Gas heaters that do not have vents are called “vent-free” models and should only be used when a door or window is open for ventilation. The reason why is that combustion products can fill the space and be incredibly dangerous to your health and safety. A handful of states (Minnesota, California, Massachusetts, Montana, and Alaska) forbid the use of gas heaters for safety reasons.
Electric space heaters are usually portable and can be moved from room to room. These kinds of space heaters use electricity to power a heating element, similar to how a toaster or clothes iron works. Electric space heaters are usually very cheap to buy, but they can be costly to run because they draw a lot of electrical power. For example, a standard 1,500-watt electric space heater needs a 15-amp branch circuit, which adds a considerable amount of load to your home’s electrical grid.
One other form of direct eating system is a wood or pellet stove. These kinds of systems are typically used in rural areas that may not have hookups to a local electrical or gas grid. Wood and pellets are usually much cheaper than gas or electricity, but burning wood releases many pollutants into the air. Newer models of wood stoves burn much cleaner, and pellet stoves are generally less polluting.
Solar heating systems are one of the newest or oldest heating systems, depending on how you look at it. People have been using direct sunlight to heat their homes virtually forever. Modern solar systems are efficient and powerful enough to match the output of gas and electric-powered heating systems.
Modern solar systems use solar panels to transform sunlight directly into heat energy. Solar panel power can be combined with pretty much any kind of heating system to power its distribution. For example, solar water heating systems use energy gathered from solar panels to heat water and distribute it through your house, just like a gas or electric boiler. Solar systems can also be passive, relying on gravity to distribute heat or active and use pumps and other electrical systems.
Another solar-powered heating system is solar space heaters. These kinds of direct eating systems gather sunlight to power a heating element. This thermal energy is then dispersed naturally or through active mechanisms such as pumps. Again, these kinds of heating systems tend to be very efficient because they have virtually no fuel costs.
Solar systems are highly efficient and virtually have zero fuel costs, but they tend to have a very high upfront cost. Installing a solar panel array and integrating it into your electrical grid can cost a lot of money, but sunlight is a free resource. Modern solar heating systems can cut your heating costs by up to 70% a year.
There are several other subtypes of heating systems that differ based on their exact distribution methods and power source. However, the ones we have covered include the most common heating systems used in modern homes. Out of all of them, the most common kind you will run into is probably furnace systems that use forced air distribution, but other kinds such as zone heating are becoming more popular. Solar systems are probably still the most uncommon, but they are quickly becoming more popular due to their efficiency and environmentally friendly nature.