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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?

From a safety and energy efficiency perspective, your best option is 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, no room air is required for combustion, there is no opportunity for heated room air to escape out the vent, so the units are also more energy-efficient. And because direct-vent units have a sealed firebox, they are generally safer.

A second common option is natural draft venting. In this case, a vertical chimney is used 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.

Less common is the power venting option, in which an electrical fan is used 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.

And then there's a technology to avoid at all costs - the so-called vent-free gas fireplace or the gas logs. As the name implies, these units offer no venting capacity - 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. If someone gives you a sales pitch about a vent-free fireplace, your response should be a simple but emphatic NO THANKS!