Heating Systems: Forced-Air, Radiator & Electric

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

You probably don't give much thought to your home heating system - unless of course, it breaks down. This lesson will explore some popular home heating systems including forced-air, radiators, and electric heaters so you can learn all about home heating.


When man discovered fire, all sorts of problems were alleviated. Fire had tons of nifty uses from cooking food, to helping us see after the sunset, to keeping us warm. Although things have changed quite a bit from those days, our dependence upon it has not. Now I could go on and on about the many uses of fire, but this lesson will focus on the 'staying warm' aspect of fire.

Unfortunately, it isn't always feasible to have an open fire burning inside of our homes, so (as clever humans), we have come up with some ingenious ways to stay warm without burning our homes down - well, most of the time. So while an open fire is sometimes used when you go camping, this lesson will focus on heating systems that don't depend on open fires including forced-air, radiators and electric heaters.


Let's start with one of the most common heating systems in the United States, which heats approximately 35 million homes. Forced-air heaters have a furnace, which can be operated through natural gas, electricity or oil, that heats up air. This hot air travels through a series of ducts to registers, which allows the air to blow into the room. Forced-air heating systems depend upon convection in order to heat your home.

The arrow is pointing to a heating duct

Hot air blows out through the register

A quick note on convection before we move on. Convection is the transfer of heat, which results in the circular movement of air (or liquid, but our focus here is air). The forced-air heating system heats the surrounding air by blowing hot air out of the registers. This increase in heat energy causes the air particles to bounce around more and get further apart, thus becoming less dense than the surrounding air. This less dense air rises. Eventually it will cool again and the particles will come closer together and become dense again. This dense air sinks, where it will get heated up again and the cycle repeats itself.

An overview of convection: The red arrows depict hot air, the blue arrows cold air


Let's move on to another popular heating system, or the radiator. Radiator heaters have been around since the 1800s and are a popular choice for many home-heating systems today. There are a couple of types of radiators, but we are going to focus on steam radiators, which work by utilizing a boiler. The boiler heats water and causes it to boil, thus creating steam. This steam travels through a set of pipes to the radiator and heat is transferred to the air through convection and radiation. Remember convection? It's a little different from the forced-air system though because, in this case, hot air isn't getting blown into a room. Instead, the hot radiator warms the surrounding air.

A radiator

Radiators can also heat your house through radiation, which is the transfer of heat through electromagnetic waves. This is different than convection because convection required the presence of particles for the heat transfer.

Okay, back to the steam radiators. After the steam cools and condenses, or changes back to a liquid, it travels back to the boiler where it gets reheated.

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