Do I need a chimney for a gas fireplace?
The four setups
- Gas logs in a wood fireplace. Vented gas logs use the existing masonry chimney, and the damper must stay open or be clamped open. The chimney still needs a sound liner, cap and flashing.
- Natural vent (B-vent) fireplaces. They draw room air and send exhaust up a double wall B-vent pipe that runs vertically through the roof, much like a small chimney.
- Direct vent fireplaces. A sealed firebox pulls outside air in and pushes exhaust out through a pipe within a pipe. The vent can exit horizontally through an exterior wall or vertically through the roof, which is why direct vent units are popular in homes without a chimney.
- Vent-free fireplaces. These burn with no vent at all. Some jurisdictions restrict them and manufacturers limit room size, so check local code and the installation manual first.
The roof side
A wall-vented direct vent fireplace puts no hole in your roof, which removes a future leak point. A roof-vented pipe needs a flashing collar woven into the shingles, a storm collar sealed to the pipe above it, and the listed termination cap at the height the manufacturer and code require. If the vent rises through a framed chase, the chase needs its own flashing and a sloped cover.
Gas appliances fall under the fuel gas and mechanical codes, and a new gas line and appliance usually require a permit and inspection from your city or county. Have a licensed gas installer size and route the vent; a roofer handles the flashing around it. If you remove an old masonry chimney after switching to a wall vent, the roof opening has to be framed, decked and shingled to match. See roof flashing explained and roofing permits in Georgia.