Natural Gas Heating Systems
Consumers strongly prefer natural gas heat because it is comfortable, convenient, reliable and efficient. Today's heating systems offer incredible choices to contractors, builders and homeowners, from top-of-the-line furnaces that achieve efficiency levels of more than 90 percent, to moderately priced units that meet or slightly exceed the minimum efficiency standard of 78 percent, so that customers don't have to pay for more efficiency than they need.
Natural gas heat feels warmer than heat produced by an electric heat pump. Natural gas heat is delivered from forced-air systems at temperatures ranging from 120-140 degrees Fahrenheit. In contrast, the air from an electric heat pump is typically delivered at 85-95 degrees Fahrenheit warm enough to heat a room, but cooler than the average human skin temperature of 98.6 degrees Fahrenheit.
Types of Heating Systems
Forced Air Systems
The most common furnace is a forced-air central heating system that uses a natural gas burner to heat air. Cool air is drawn into the system, moved into a heat exchanger where it is warmed by the gas burner and then circulated by a blower or fan through the home s ductwork. A forced air system can also include items such as electronic air filters, electric cooling equipment and a humidifier or dehumidifier.
The combustion of natural gas produces byproducts of water vapor and carbon dioxide, which are the same elements exhaled when people breathe. These flue gases must be vented to the outdoors. Wall vents can be used for mid- and high efficiency natural gas forced-air furnaces, thus eliminating the need for the standard chimney and/or chimney liner.
Radiant Water-Based or Hydronic Heating Systems
Hydronic or hot water systems have a gas boiler that creates steam or hot water, which is then circulated through the home in pipes or tubes. These heating systems can incorporate radiators, radiant floor systems or baseboard units. Boilers or hydronic systems use the same type of venting as with forced air systems.
Combination Water Heating & Space Heating Systems
Combination systems are designed primarily for use as a forced air heating system but can also be adapted for some hydronic baseboard systems. A natural gas burner heats water to be used and stores it in a tank, just like a regular water heater. To provide space heating, a pump sends some of the hot water through a heated metal coil. A fan blows air over the heated coil and through the ducts in the home.
Natural gas space heaters are a good choice for rooms that aren t used often, for areas of the home that need a heating boost and for room additions. These compact, energy-efficient units can be mounted on a wall, contained in baseboard units or place like a fireplace or stove unit. They are sized to heat just one room, or several. They are often directly vented to the outside using conventional chimneys or flue vents, but unvented models are also available.
A radiant room heater has a glowing panel that warms people and surfaces in its direct path. A convective heater warms the air in the room. Some convective heaters use the natural circulation created in the room to distribute heated air and others use a small fan or blower to distribute the warm air.
Efficiency and Operating Costs
The energy efficiency of any heating system is measured in its Annual Fuel Utilization Efficiency (AFUE). This is the ratio between the amount of energy that goes into the system and the amount of energy that comes out as usable heat. It takes into consideration heat lost during start-up and cool-down, as well as the unit s efficiency while it is running. The higher the AFUE, the more efficient the furnace. New furnaces must operate at 78 percent efficiency or better; some high-efficiency natural gas heating systems use 98 percent of their energy input.
To determine which model is most appropriate, builders and consumers should compare both the initial cost to buy and install the system and its average annual operating costs. A natural gas heating system may cost more to purchase than an electric system, but it often costs less to operate. In 2001, for example, it cost less to operate even a low-efficiency natural gas furnace than to operate an electric heat pump, and nearly three times as much to heat a home with an electric-resistance furnace as it did to use a high-efficiency natural gas furnace.