Do gas fireplaces need a chimney?

Gas fireplaces do not need a traditional masonry chimney — but they do require some form of venting, and the type depends on which style of gas fireplace you choose.

The Three Venting Options

The most common choice for new installations is a direct-vent gas fireplace. These use a sealed combustion system with a double-wall pipe that pulls fresh air in from outside and exhausts combustion gases back out — all through the same unit. The pipe can run horizontally through an exterior wall, which means you can install a gas fireplace almost anywhere in your home without a chimney at all. This is the safest and most energy-efficient option.

A natural vent (B-vent) fireplace does require a vertical flue that rises through the home and exits through the roof — similar in concept to a chimney, though it uses a metal liner rather than masonry. These are less common in new installations because they draw heated indoor air for combustion, making them less efficient.

The third option is a ventless (vent-free) fireplace, which requires no venting at all. However, ventless gas appliances are actually prohibited in many jurisdictions in Ontario, and TSSA requirements around these units are strict — confirm with your licensed technician before considering this route.

Ottawa-Specific Context

In Ottawa, gas fireplace installation requires a TSSA permit, and the work must be performed by a licensed gas technician (G2 or G3 licence). The City of Ottawa may also have additional requirements depending on your home type and where the fireplace is being installed. Installation costs in the Ottawa market typically run $3,000 – $6,000, depending on the unit, venting complexity, and gas line work required.

Safety Note

Any gas appliance installation is not a DIY project — improper venting can lead to carbon monoxide buildup inside your home, which is odourless and potentially fatal. Always ensure your home has working CO detectors on every level, especially near sleeping areas.

If you're thinking about adding a gas fireplace to your home, Ottawa HVAC Pro would be happy to walk you through the options and provide a free estimate based on your specific space.