What Is Forced Air Heating?

When you turn on the thermostat in your home, adjust it to a comfortable setting and feel warm air blowing from the vents, you’re utilizing the forced air heating system in your home. Not all homes have forced air heating; many have heat supplied by radiators, baseboard heaters or hot water pipes embedded in the floors or wall.

Forced air heating is far more common, however, and for three reasons: “It’s cost-effective, easy to use, and allows for an AC system to incorporate directly into the same system,” says Korey Gregory, a superintendent for ASAP Restoration.

Because the warm air from a forced air heating system originates from a central heater either a furnace or a heat pump people often refer to it as a Central Air or HVAC (Heating, Ventilating, Air Conditioning) system. This helps avoid confusion between a whole-house heating system and a high-powered portable electric or gas heater that uses its own internal blower to distribute heat. These portable heaters also “force” warm air into the living space, and as Gregory pointed out, are what folks in some parts of the country think of as forced air heaters.

So, to be clear, we’re talking about central forced air heating systems in this post not portable ones.

I’ve had my share of maintenance experience with central forced air systems over my time as a homeowner. Without TLC, an HVAC system won’t work as expected, wasting energy and driving up your utility bill. “HVAC systems are complex, require permits and specialized tools, and involve safety hazards,” says Tim David of Airlucent.

Even so, you can (and should) take the time to understand your home’s system so you can perform routine tasks like cleaning internal parts and changing filters.

About the Experts

• Korey Gregory is the Superintendent for ASAP Restoration, LCC. He has more than 17 years of experience in the construction industry and currently manages HVAC installs and completes final walkthroughs with customers.
• Tim David is the CEO of Airlucent.com. He has more than 25 years of experience as an HVAC technician and now trains new technicians.

What Is Forced Air Heating?

A forced air heating system is one that heats air in a central location. It uses a fan or blower to distribute the heated air throughout an entire building via a ductwork system. The heat source may be electric heating elements, a heat pump (which also uses electricity), or the combustion of a fuel, such as natural gas, propane or heating oil.

How Does Forced Air Heating Work?

As Gregory puts it: “Forced air heating takes the air inside of a property and passes it over a heating element to warm it up, and then recirculates it throughout the home. When the air is recirculated, it passes back over the heater again and again until the ambient temperature of the room the thermostat is in gets to the desired level.”

The various parts of a forced air heating system must be choreographed to bring a room to the desired temperature and keep it there. This is the job of a central control panel that responds to signals from the thermostat and sends prompts to the various system components to switch on and off. Every system also includes a number of safety sensors and switches designed to shut everything down in the event of a malfunction.

Parts of a Forced Air Heating System

A forced air heating system needs a heat source, a fan to circulate air and ductwork to deliver conditioned air throughout the building and return air to the heater for further conditioning. Systems vary according to fuel, but most of them include these components:

• Heat source: Heat may be generated by a gas or electric furnace or a heat pump. Furnaces that burn a fuel do so in a sealed combustion chamber.
• Inducer fan: Switches on to clear gases from the combustion chamber before the furnace starts up. It continues running until the furnace shuts down. This is an increasingly common component of gas furnaces.
• Heat exchanger: “This is usually a steel or cast iron box that is responsible for transferring the heat to the air that you circulate through the space,” says David. “Think of it as the heart of your heating system.”
• Plenum: A large enclosed area above the heat exchanger where warm air collects before distribution.
• Supply and return ducts: A network of steel or fiberglass supply ducts deliver air through the building via adjustable vent openings called registers. Air drawn through a return register circulates back to the heat source through the return ducts to be reheated.
• Blower or fan: Blows heated air through the supply ducts and sucks unconditioned air through the return duct for reheating.
• Thermostat: Usually located in a central area, the thermostat monitors room temperature and switches the system on and off as needed.
• Exhaust vents: Combustion gases are released outside the building through the exhaust vents. High-efficiency furnaces also need a drainage system to direct condensation outside.

Forced Air Heating Pros and Cons

According to Gregory, “Forced air heating systems are popular because they are cost-effective, easy to use, and allow for an AC system to incorporate directly into the same design.” However, there are also some drawbacks to consider before going all-in on a forced air system.

Pros

• It provides heat quickly: A well-designed system can warm a room quickly; some HVAC pros claim in as little as five minutes.
• It’s controllable: You can regulate heat flow to certain parts of the building by opening and closing registers.
• It’s affordable: Forced air systems are less expensive to install than radiant heat systems that use a boiler.

Cons

• It can cause low humidity in your home: “Because furnaces heat air,” says David, “they can sometimes lead to a reduction in indoor humidity, potentially causing dry air issues.” Dry air can damage wood floors by causing shrinkage and gapping. It can also adversely impact people with respiratory health issues.
• Leaking ducts: Leaks in a forced air heating system’s ducts can reduce heating efficiency and increase monthly heating bills.
• It can get noisy: The system’s fans produce an audible hum that usually isn’t loud enough to be problematic, but it can become so if the system isn’t maintained.

How to Maintain a Forced Air Heating System

Because of the need to test and possibly replace sensitive electronic equipment, most forced air heating problems need professional attention. Most manufacturers recommend a yearly professional tune-up to keep a system in top shape. However, homeowners can and should do these simple tasks themselves:

• Replace air filters yearly or every three months during periods of heavy use.
• Switch off the system in the fall and manually clean dust from the blower motor and the inside of the plenum.
• Inspect the ductwork periodically for leaks.

Sources

• Bayhealth.org: “Effects of Dry Winter Air and Indoor Heating on our Respiratory Health” (2020)

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