How Fireplaces Work

If you're looking for a fireplace that gives you both efficiency and the pleasure of watching the flames dance, you might consider a gas model. You can't roast marshmallows in them, but you'll have the advantage of a clean and convenient source of heat.

A modern gas fireplace emits no smoke and vents its waste gases to the outside through a tube in the wall rather than up a chimney. It incorporates air-movement channels that maximize the warmth supplied to the house. The fireplace consists of incombustible "logs" covering gas vents, and the fire itself burns behind glass doors. It gives off both radiant and convected heat and provides an experience similar to an open fire [source: Berendsohn].

One benefit of a gas fireplace is that it may help lower heating bills. It lets you heat the room you are spending time in while you keep your thermostat low and the rest of the house cooler. You stay toasty and your furnace gets a rest. Most gas fireplaces take advantage of sealed combustion. Their doors have gaskets that block all air. The fire draws air outside air through a pipe to support combustion, so no warm room air is drawn out of the house.

If you want to add a fireplace to an existing home, a gas fireplace makes sense. Because it doesn't require a massive masonry hearth and chimney, it can easily be included in a new family room. You sacrifice much less floor space and still have a fire to look at. You can also buy a gas fireplace insert that fits into a traditional fireplace hearth and boost its energy efficiency. As with its wood-burning counterpart, the gas insert has its own flue that snakes up the masonry chimney.

Because gas burns very cleanly, there are even vent-free fireplaces on the market. In this case, the combustion products -- carbon dioxide and water vapor -- simply enter the room, along with all the heat produced. Although highly efficient, they are also subject to debate. In a tight home, a vent-free fireplace can deplete oxygen or create an excess of moisture. The American Lung Association warns buyers to be careful of the emissions given off by vent-free appliances [source: American Lung Association].

Gas fireplaces are easy to use and require little maintenance. Some come with a remote control, so that you can adjust them from across the room. You will occasionally have to remove dust, soot and carbon buildup from the logs and make sure the door gaskets are intact. As with any gas appliance, if you smell gas, turn off the supply and call an expert.

Because they involve open flames, all fireplaces -- even gas ones -- create some danger. The next section will talk about how to use a fireplace safely.