Does a Gas Fireplace Need a Chimney?

When the weather outside is frightful, the dance of flames in an interior fireplace can be more than delightful. A working fireplace can provide much-needed warmth as well as seasonal ambiance, and gas fireplaces are a choice for many homeowners.

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What Is a Gas Fireplace or Gas Logs?

Before considering your options for venting a gas fireplace, make sure you know what type of gas heating source you need. When people say they have a gas fireplace, they may mean:

• A gas fireplace, which is a stand-alone gas-powered unit that generates a good deal of heat. The fireplace includes a metal box inside another metal box; gas burns in the interior, heating the air between the boxes. That heat radiates into the surrounding room.

• Gas logs, which are decorative ceramic logs with a gas burner. Holes in the logs allow gas to burn, creating the impression that the logs are burning in the fireplace. Gas logs don't usually generate as much heat as an actual gas fireplace.

• Gas insert, which is a box-in-box enclosure that's inserted into an existing fireplace. Gas inserts let you convert a wood-burning fireplace to a gas fireplace.

Does a Gas Fireplace Need a Chimney?

Whether you need a chimney for a gas fireplace depends on the type you have and how it was installed.

Direct Venting Fireplace

Direct vent fireplaces are stand-alone sealed systems. Often, the gas-fueled fire burns behind a glass front, so you don't have direct interaction with the flames. The system includes pipes that pull fresh air from outside to feed the fire and vent air outside to reduce contamination in the house. Direct vent fireplaces are usually vented out of a roof or wall, much like a clothes dryer or range vent.

Ventless Gas Fireplaces

Vent-free gas fireplaces are designed not to need exterior venting. Theoretically, these systems are supposed to burn all the fuel — the gas — without emitting anything dangerous into the interior space. However, they don't always work as expected, and some concerns about carbon monoxide buildup and other air-quality issues exist. Due to those challenges, vent-free gas fireplaces aren't allowed in California and some other areas.

If you don't have an option for direct venting but are worried about code violations or safety issues with vent-free gas options, you might consider a power vent. This option uses an electric fan to push exhaust out of a small pipe, which can be installed through an existing window or exhaust route in the home.

Gas Logs or an Insert in an Existing Chimney

If you already have a chimney, you can convert it to a gas fireplace by adding an insert or gas logs. Properly installed gas logs and inserts utilize existing chimneys and flues, eliminating the need for a separate gas fireplace vent pipe.

Systems that aren't fully enclosed like gas logs are sometimes called natural vent fireplaces or B vent fireplaces. They vent naturally following the existing chimney structure and basic principles of physics. Indoor air provides oxygen necessary for combustion, and exhaust gases naturally travel up due to being hot. They're captured by the chimney pipe and vented up out of the roof.

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Can You Install a Gas Fireplace Yourself?

Always involve professionals in installing a gas fireplace, whether you're inserting one into an existing chimney or adding a direct vent option to your home. Professionals can:

• Inspect existing chimneys and fireplaces. Using a chimney for your gas fireplace requires the structure to be in working order. A chimney inspector ensures there's no damage to the structure that might create a safety hazard when you heat it. They also check to verify the chimney and flue aren't blocked and exhaust from your gas fireplace has a path out of your home.

• Ensure fireplace components work well. While gas fireplaces and logs aren't extremely complex, broken or malfunctioning parts can lead to fire dangers and health hazards. It's best to let a certified professional install and test these components.

• Connect gas lines. Even if you're installing gas logs out of the box, if you don't already a connected gas line, involve a professional for safety. In many cases, you won't be able to set up new gas services without a professional installation.