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Personal: Residential

Installing Your Gas Fireplace

Locating a fireplace for maximum benefit
Venting your gas fireplace

In a large space, such as a home, a gas fireplace is not an efficient primary heating source. An energy-efficient furnace is usually a better choice. If you plan to use a gas fireplace as a secondary heat source, however, the EnerGuide label can help you find the most efficient model for your purpose. An efficient gas fireplace can lower a home's overall energy consumption and heating bills when located in a major living area where the heat can get to other parts of the house. The EnerGuide label for gas fireplaces is found in fireplace promotional materials, such as sales brochures, or on Web sites.

Locating a fireplace for maximum benefit

If your home-building or renovation plans include an efficient gas fireplace, take some time to plan the installation so that the fireplace can effectively contribute to your heating needs. Install the fireplace in a part of the house where it will be visually attractive and where you and your family spend most of your time and will benefit the most from its warmth. This is usually on the main floor, in your family room, dining room, living room or kitchen.

The layout of your house will affect the fireplace's ability to provide heat to other areas of the house. If you are building a new home, consider a layout that focuses on the fireplace. An open design, with few walls separating rooms on the main floor, will allow heat to move from the fireplace area to other rooms. An accessible stairwell will also allow the heat to move upstairs.

Figure 1: all about gas fireplaces

Efficient natural gas fireplaces can effectively lower heating costs and improve comfort levels in homes heated by electric baseboards. The baseboards in remote rooms can keep those areas at acceptable temperatures, effectively "zoning" the house, with the gas fireplace providing most of the "comfort" heat for the rest of the home. A properly located and well-designed fireplace can meet over half the conventional heating demands of a standard house while providing a visually appealing and comfortable atmosphere.

If your house's layout is such that the best location for a fireplace is against an outside wall, try to build the fireplace inside the house envelope. If this cannot be done, look for a fireplace with an insulated outer casing. Insulation is also important for a gas fireplace insert that is installed in an existing outside wall fireplace in order to eliminate direct heat loss from the fireplace through an outside wall.

Figure 2: all about gas fireplaces

Another option to minimize heat loss is to locate the fireplace and chimney on an inside wall. By surrounding the vent with warm rather than cold air, you ensure better draft and reduce the chances that the house will become a better chimney than the chimney itself.

The House as a Chimney

An operating chimney is an enclosed column of warm air or gases surrounded by colder outside air. The warm air or gas in the chimney is more buoyant than the dense, cold outside air, so it rises, producing a natural vertical draft in the system.

In the winter, your house is also an enclosed column of warm, buoyant air that creates its own form of draft. In effect, the warm air pushes upward, creating higher air pressure at the top of the house and lower pressure in the lower levels of the house.

When an unsealed (non-direct-vent) gas fireplace has been installed in a home that has a lower pressure than outside, the house can become a more effective chimney than the fireplace chimney itself – especially if the chimney is located on an outside wall. Rather than using the chimney to release combustion gases to the outdoors, air can be drawn back under negative pressure into the home through the chimney. This reverse flow of air can cause spillage of combustion gases from a fireplace or other combustion appliances into the home, creating hazardous indoor air-quality problems.

If you must install a gas fireplace in the basement, a direct-vent unit is likely your best bet since it does not require a chimney. A direct-vent fireplace can be exhausted out the side wall of the house above the foundation, and it is sealed to prevent combustion exhaust spillage or the robbing of air for combustion from the furnace or water heater. Consider insulating the basement before you install a fireplace there. As it will be more difficult to distribute heat, consider a low-input fireplace or a unit that can have ducts to transfer the heat elsewhere.

Venting your Gas Fireplace

One of the most important decisions you'll have to make when purchasing a new gas fireplace is how it will be vented – in other words, how do you make sure combustion gases are removed from the firebox to the outdoors?

Three options are available: natural draft venting, power venting and direct venting

Figure 3: all about gas fireplaces

With a direct-vent fireplace, outdoor combustion air is drawn directly into the firebox through one pipe, while combustion products are exhausted through another. This has two important benefits. First, the sealed firebox generally makes these units safer: no room air is required for combustion. In addition, because there is no loss of heated room air out the vent, the units are more energy-efficient.

Direct-vent fireplaces are typically installed on an outside wall, with the vent running directly through the wall, although some models are approved for extended horizontal and vertical flues.

Figure 4: all about gas fireplaces

Natural draft venting uses a vertical chimney to take advantage of the fact that hot air rises, causing a natural draft of hot combustion gases up the flue to the outdoors. These units require a draft hood that uses house air to isolate the burner from outside pressure fluctuations.

Natural draft fireplaces typically use a B-vent or, in an existing chimney, an approved metal liner that includes a B-vent or a flexible metal liner.

Less common is power venting, which uses an electrical fan to assist the venting process. Power venting allows units to be installed in areas of a home where a conventional flue cannot be used. It can improve a fireplace's efficiency and will use less house air, as a draft hood is not required.

CAUTION: Avoid vent-free gas fireplaces (gas logs). As the name implies, these units offer no venting capacity. This means that harmful combustion byproducts, including possibly deadly carbon monoxide, are released directly into your home. In airtight Canadian housing, these units are not only unacceptable, they can be dangerous. They may introduce unwanted moisture into the home as well.

Figure 5: all about gas fireplaces

Venting may be either coaxial or collinear.

  • Coaxial venting uses two concentric pipes. The outer pipe brings combustion air in from the outdoors, and the inner pipe exhausts the combustion products. This is the method commonly used for sidewall venting.

  • Collinear venting uses two completely separate pipes, one to supply outside combustion air and the other to exhaust combustion products. This method is most often used where there are space limitations when an existing fireplace and chimney have been retrofitted with a gas insert or where long vent distances and cold temperatures make condensation and vent icing a potential concern.

To be installed in an energy-efficient R-2000 home, a gas fireplace must be either direct-vented (sealed) or power-vented. This provides an additional level of protection against spillage of combustion products and helps increase the appliance's efficiency.