Heating Systems Explained

An HVAC system.

It doesn't matter if you live in a warm area of the country like Florida or California or in one of the cold and snowy regions up North, you need to know something about home heating systems. Home heating systems can range from very simple (like a small space heater for a single room) to complex multi stage systems to heat large homes with thousands of square feet. Heating systems can use many different types of fuels for their heat source (gas, oil, electricity, wood, solar power) and have different ways of distributing the heat (forced air, hot water, steam heat, radiant hot water). No matter their differences, all home heating systems have some things in common.

Basic Components

All heating systems work on the same principle – heat moves from a warm object to a cooler object. All heating systems are made up of a number of components that all need to work together for the system to function properly.

Heating systems need something that produces heat (commonly an oil or gas-fired burner) and a heat exchanger (where the heat from the furnace is transferred to the air or water). They also need a distribution system to carry the hot air or water throughout your home and finally some form of a controller (a thermostat or aquastat) to measure the heat in your home and tell the system when it needs to produce heat and when to shut off.


One other commonality between all heating systems is they all cost money. In fact, the Environmental Protection Agency estimates that between 30% to 50% of a home's energy consumption goes to heating the home. It's important you understand how different home heating systems work as well as have some idea of the strengths and weaknesses of different systems so you can make informed choices about your home heating system.

While there are numerous types of home heating systems ranging from old fashioned wood-burning stoves to relatively new and emerging systems such as geothermal heat pumps that gather heat trapped in the air or in the ground and bring it into your home, or solar systems that capture heat from the sun's rays, turn it into electricity and use the electricity to generate heat for your home, in the interests of clarity and simplicity, here we'll stick to discussing air and water-based systems that use furnaces and boilers powered by gas, oil, or electricity.

Heat Sources

Gas (either propane or natural) and oil are the most commonly used fuels for furnaces or boilers in both warm/forced air systems and water or steam-based heating systems.
A few years ago electricity was also a relatively common heat source for both electric furnaces and electric baseboard heating, however, the cost of electricity relative to gas and oil has made it less common in recent years.
Electric baseboard heating can be thought of as a type of hybrid, since it combines the heat source (electricity) and the distribution system (baseboard heaters) into a single integrated system.
The relatively high cost of electricity and the scarcity and probability of rising prices for fossil-based fuels makes it increasingly important to have an efficient properly sized heating system in your home.

Warm Air Heating Systems

In a warm air heating system when the thermostat calls for heat, the furnace turns on producing heat. Next, a fan or blower comes on and pushes air through the furnace's heat exchanger then out through the distribution system (heat ducts) to all parts of your home where it gives up its heat to the cooler air. After giving up its heat the now cooled air returns to the furnace through the second set of air ducts (cold air returns) where it is reheated and sent out to once again carry heat to your home. The system operates in a continuous cycle until the temperature in your home matches the thermostat setting and it tells the furnace to shut off. Forced air systems are examples of convection heating that uses moving air to provide heat to a home.

Hot Water Systems

Hot water (and older steam) heating systems work on the same closed circulating principle as warm air distribution systems except they substitute water for the air. The water is stored in a holding tank where it is warmed up and a water pump (rather than a fan) moves the warm water to the radiators or baseboard heaters where it gives up its heat then returns to the furnace to be reheated. A component called an aquastat provides the temperature measuring function of a thermostat.
Hot water heating can be implemented in a number of ways such as old fashioned radiators, baseboard heating, where the hot water is circulated through baseboards or sometimes as in-floor radiant heat where the warm water circulates in tubes under the floor, warming both the floor and your home by the heat radiating through the floor.
Some hot water systems combine home heating with water heating by using a common boiler to provide both the hot water supply for washing and cleaning in the home as well as the water used to heat the home, eliminating the need for a hot water heater.
Hot water systems are radiant heating systems where the heat radiates out into a room and there is no actual air movement in heating your home.

Forced Air Heating

Forced air heating is very common and relatively inexpensive. The air can be filtered, humidified and dehumidified for comfort. Existing distribution ductwork can be used to carry cool, air conditioned air in the summer

In forced air heating systems, however, moving air will carry dust and allergens throughout the home. Convection systems that use moving air often have cold areas since heat rises to the top of the room and the air circulation in a room may not be balanced.

Steam/Hot Water Radiators

How water radiators provide a very constant and even temperature. They use radiant heating (rather than moving air) and most people find radiant heating more comfortable.

Many people think of radiators as old fashioned and unattractive. Radiators take up space in a room and restrict furniture arrangement. The system has no in place ductwork to carry cool air in the summer so air conditioning a home is more expensive.

Hot Water Baseboards

Hot water baseboards are very quiet and provide constant, radiant heat that allows temperature control in individual rooms.

Baseboard heaters can't be covered with furniture or drapes, however, and while less obtrusive than radiators, baseboard heaters still restrict furniture placement.

In-floor radiant heating

Radiant heating is very quiet and comfortable by providing constant, radiant heat. Individual rooms heat slowly, though, since the floor itself must heat up before the room will feel warm. It is expensive to install as a retrofit and it can be hard to reach water pipes for maintenance. It does not have any ducts for air conditioning.

Things to Look For

There are a myriad of things that can impact on the right heating system for your home. For example, where you live in the country, the size of your home, the amount of insulation in your walls and ceiling, your family life style and how they use the heating system will all have an impact on determining the right size and type of system for you. Fortunately, there are some common factors to help you make your decision.

Proper sizing is important. Having a furnace that's too small will mean it needs to work extra hard to keep your home warm, wasting fuel and causing the furnace to wear out sooner. Alternatively, a furnace that's too large will cycle on an off more often than a properly sized furnace, making it inefficient and costing you money at the time of purchase and also during the life of the furnace. Have a contractor do a specific heat requirement calculation for your home and don't accept a quote based strictly on the square footage of your home.

All new furnaces have an Annual Fuel Utilization Efficiency (AFUE) rating that tells you how efficient they are at extracting heat from the fuel they burn (the higher the number the more fuel efficient the furnace will be). Since 1993 the Federal government has required all furnaces to have an AFUE of at least 80% and high efficiency furnaces that are over 95% efficient are available.

Some higher efficiency furnaces have two stage burners that allow the furnace to operate at lower burn rates so they burn less fuel when the demand for heat is low. When more heat is required, the second stage kicks in to meet the higher heat demand. This design provides significant fuel savings over the life of the furnace.

Helping Your Heating System

You can help improve the efficiency of your home heating system in a number of ways. You can improve your home's energy efficiency by adding insulation to your walls and attic. Blown cellulose insulation is a relatively easy to do method for adding incremental insulation to existing walls and both fiberglass or blown cellulose are great insulation options for increasing attic insulation.

Seal around doors and windows with weather stripping and caulking to keep cold drafts out. Locking windows will improve your homes efficiency by closing them tighter and keeping cold drafts out.