Gas fireplaces are a popular type of fireplace to be installed within a home as the different options available for gas fireplaces allow them to be installed in many locations around a house.
Certain types of gas fireplace will sit within an existing masonry fireplace and utilize a chimney, some will vent directly out of a home and many won’t need any form of direct ventilation at all, and so what types of gas fireplace have a flue?
Natural vent gas fireplaces may use an existing chimney flue to vent waste air, direct vent gas fireplaces will have a flue in the form of a direct vent going straight out of a home and ventless gas fireplaces won’t have any form of flue.
Our own gas fireplace is a natural vent type meaning that it sits within an open masonry fireplace and utilizes the existing chimney flue for venting.
Not all gas fireplaces will have or require a flue, but some will require them in order to operate safely.
To explain whether gas fireplaces have a flue we’ve put this article together to discuss:
- Whether gas fireplaces have a flue and why.
- Which types of gas fireplace need a flue, and which don’t.
Do Gas Fireplaces Need A Flue?
Natural vent gas fireplaces may not have a flue but will use the existing chimney flue to vent waste air from a home. Direct vent gas fireplaces will need a flue that vents air directly out of a home, and ventless gas fireplaces won’t need any form of flue.
Whether a gas fireplace has a flue or not will depend on whether the fireplace is vented or ventless.
If a gas fireplace is vented it means that waste air produced by the fireplace is allowed to leave a home.
If a gas fireplace is ventless then there’s no external form of ventilation and all waste air from a ventless gas fireplace is released back into a home.
Ventless Gas Fireplace Flue
Ventless gas fireplaces don’t have or require a flue because they’re not designed to vent either clean or waste air to or from a home.
A ventless gas fireplace, also known as vent-free or flueless, is designed to burn the fuel so cleanly that they’re rated for indoor use without any form of direct external ventilation such as a flue. Ventless gas fireplaces use the oxygen within the air of a home to feed the fire and the by-products consist mainly of Carbon Dioxide and water vapor.
As a result, ventless gas fireplaces can be far more versatile compared to other types of gas fireplace and can be placed in many more locations around a home, and not simply where a flue needs be used to vent waste air such within an existing masonry chimney or up against and external wall.
Although ventless gas fireplaces won’t need any form of flue for direct venting, depending on your area of residence and respective building codes and regulations, an external air vent may need to be installed into the room to help keep oxygen supplies at an acceptable level.
Ventless gas fireplaces therefore do not typically need any form of flue because no external venting arrangements are required.
Vented Gas Fireplace Flue
While ventless forms of gas fireplace don’t need a flue, vented gas fireplaces will need a form of flue in order to be safely installed within a home.
Vented gas fireplaces can typically be found in two main forms:
- Direct vent gas fireplaces
- Natural vent gas fireplaces
Direct vent gas fireplaces are sealed system where both the air used for combustion and the waste air is vented directly to and from the outside, and the air within a direct vent gas fireplace is completely separated from the air within a home.
Direct vent gas fireplaces therefore need a form of flue in order to function.
The air intake vent for a direct vent gas fireplace typically extends horizontally out the back of the fireplace and through an external wall of a home to the outside. This allows a direct vent gas fireplace to take air directly from outside.
The exhaust vent for a direct vent gas fireplace allows waste air from the combustion chamber to be vented directly outside and prevent it from mixing with the air in a home.
This exhaust vent for a direct vent gas fireplace can:
- Extend out horizontally through an external wall next to the intake vent.
- Extend out the external wall of a home but further up the wall in relation to the intake vent.
- Extend vertically up through the roof.
Which form of flue setup is chosen for a direct vent gas fireplace will differ between each situation but can be commonly be seen as a dual vent arrangement where both the intake and exhaust vents sit next to each other through an external wall of a home.
Although direct vent gas fireplaces require both intake and exhaust vents to the outside of a home, they are popular options for gas fireplaces because the air associated with the use of a direct vent gas fireplace is kept completely separate and sealed off from the air within a home. This can mean that direct vent gas fireplaces can produce fewer noticeable smells compared to other types of gas fireplace.
Therefore, direct vent gas fireplaces need a flue that either extends horizontally out through an external wall of a home or vertically up through the roof.
The other main type of vented gas fireplace is natural vent gas fireplaces.
Natural vent gas fireplaces, also known as B-vent, traditionally sit within masonry fireplaces and utilize the associated chimney for removing waste air from a home.
A natural vent gas fireplace will:
- Use air within a home to feed the combustion inside the gas fireplace.
- Exhaust waste air indirectly out of a home using a natural draft movement of air up a chimney.
Whether a chimney used as part of a natural gas fireplace insert for a masonry fireplace will have a flue liner or not may depend on the situation and local building codes and regulations.
Our own gas fireplace is the natural vent type.
It sits within our living room existing masonry fireplace and utilizes the chimney as a flue to remove waste air from the house.
There is an opening at the top of our natural vent gas fireplace above the burner tray and fake coals. As warm air from the fire rises it’s pulled up through this vent hood into the chimney thanks to the draft, which allows the waste air to leave the house via the chimney.
As this gas fireplace was already installed in the house when it was bought, we’re currently unsure as to whether there’s a flue liner installed within this chimney. Either way, the gas fireplace isn’t directly connected to the chimney and so waste air indirectly leaves the house through this chimney.
This masonry fireplace also doesn’t have a damper installed.
If there was a damper installed in this chimney then it would need to be open and stay open while the gas fireplace is installed within this masonry fireplace.
A natural vent gas fireplace relies on the natural movement of air up a chimney and so any damper located within a chimney must be open. See our compete guide to dampers for more information.
Natural vent gas fireplaces therefore typically have no direct flue connection but indirectly use a chimney flue as a way to vent waste air from a home.