Gas Fireplace Vent Hood

Do Gas Fireplaces Need To Be Vented?

In Gas Fireplaces by James O'KellyLeave a Comment

Gas fireplaces are still a popular form of fireplace to be installed into homes, partly thanks to their versatility in where they can be located in a house.

This versatility can be due to the various venting options offered by modern gas fireplaces, which include the ability to vent from inside your home or directly from outside.

Natural vent gas fireplaces need to be vented using a traditional masonry chimney with flue liner, direct vent gas fireplaces need to be vented directly from the outside and ventless gas fireplaces don’t need to be directly vented.

We have a natural vent gas fireplace where a gas insert was installed into an existing masonry fireplace to transform the fireplace from wood burning to gas.

We’ve therefore discussed and explained in more detail below using our own natural vent gas fireplace as an example:

  • Whether gas fireplaces need venting.
  • What the venting requirements are for each different type of gas fireplace.

This article primarily goes into the venting requirements for gas fireplaces, which covers how each different type of gas fireplaces gets its air for combustion but also touches on how waste air can be exhausted.

For more information on whether a gas fireplace needs a chimney see our separate article here.

Do Gas Fireplaces Need Venting?

Not all gas fireplaces need venting. Both natural vent and direct vent gas fireplaces need venting, which exhaust air up a chimney and through the wall to the outside respectively. Ventless gas fireplaces don’t need venting.

Whether gas fireplaces need venting can be a bit of a confusing subject because there are a few different types of gas fireplace to choose from and all have different venting requirements.

In summary, there are three main types of gas fireplaces, each with different venting arrangements:

  • Natural vent gas fireplaces
  • Direct vent gas fireplaces
  • Ventless gas fireplaces

Natural vent gas fireplaces take air from the room and exhaust waste gases up through an existing masonry chimney (that may have a flue liner installed) or flue.

Direct vent gas fireplaces take air directly from outside a home and also exhaust waste air directly outside.

Ventless gas fireplaces intake air from a home and exhaust air back into the room.

Natural Vent Gas Fireplace Venting Arrangements

Natural vent gas fireplaces don’t need any special air intake arrangements and simply take air from the room it’s located in to feed oxygen to the flames.

Natural vent gas fireplaces are typically gas fireplace inserts that are commonly installed within existing masonry open fireplaces to convert the fireplace from wood burning to gas.

As these types of gas fireplaces are located within masonry fireplaces that haven an existing chimney, waste air from a natural vent gas fireplace is exhausted up the chimney.

Our own gas fireplace is naturally vented.

Gas Fireplace
Our gas fireplace is naturally vented and take air from the room and waste air leaves up the chimney through through the hood at the top of the fireplace

This gas fireplace insert had already been installed into an existing masonry fireplace when the house was bought. We’re usure of exactly how old this gas fireplace is but the user manual dates back to 2004.

This particular gas fireplace is a natural vent gas fireplace because:

  • The fireplace takes air from the room/home.
  • The fireplace exhausts waste air up the existing masonry chimney.

There’s no glass front doors or sealed chamber (common with newer types of gas fireplaces) and so the gas fireplace is completely open. This allows the fireplace to vent fresh air from the air within the room.

Gas Fireplace Coals
Our particular gas fireplace isn’t sealed and vents air directly from the room

Natural vent gas fireplaces also exhaust waste air up through the existing chimney, usually through a form of flue liner, or a separate flue.

We’re currently unsure of whether our own chimney has a flue liner installed, but waste air from the gas fireplace rises up through the hood opening at the top of the fireplace and then up the chimney.

Gas Fireplace Vent Hood
Waste air leaves the gas fireplace up the chimney through the hood vent

This natural gas fireplace was installed within an existing masonry fireplace located on an internal wall of the home and so isn’t directly connected to the outside of the home apart from through the chimney.

If you have a damper located in your chimney then you’ll need to ensure that it remains open when using a natural vent gas fireplace. You can read more about dampers in our complete guide to dampers here.

Therefore, gas fireplaces in the form of natural vents gas fireplaces do need to be exhausted out of a home by utilizing an existing chimney or flue but can be vented using the air from within the room.

Direct Vent Gas Fireplace Venting Arrangements

Direct vent gas fireplaces differ to natural vent gas fireplaces in that both the air used for combustion and the waste air are vented directly to and from the outside of a home.

These direct vent gas fireplaces can be more of a common type of gas fireplace as they don’t require the use of a masonry chimney in order to facilitate being able to use the fireplace.

Direct Vent Gas Fireplace
A direct vent gas fireplace will require a dual vent directly through an external wall for both venting and exhausting of air

Instead of venting the air from the room like natural vent gas fireplaces, direct vent gas fireplaces take air straight from the outside using a vent pipe.

A direct vent gas fireplace can also exhaust waste air through the same vent pipe, or depending on the situation or configuration of the gas fireplace, there may be another direct vent located further up the wall or going straight up through the roof.

It’s common to have a dual vent/exhaust for direct vent gas fireplaces that go straight through the exterior wall of a home out the back of the fireplace unit.

This helps to make direct vent gas fireplace more versatile when it comes to choosing where to place a gas fireplace in a home as having an existing masonry fireplace in which to put one isn’t a necessity.

Direct vent gas fireplaces are enclosed systems where the fire chamber is kept within a sealed environment behind closed doors, meaning that all air, both fresh and waste, used as part of the operation of a direct vent gas fireplace doesn’t interact the air inside a home.

Heat from a direct vent gas fireplace can be radiated out into the room, or if the unit has an integrated blower then air from the room can be circulated through the gas fireplace and heated up as it passes around the combustion chamber.

Therefore, gas fireplaces in the form of direct vent gas fireplace do require venting in the form of direct vents through an external wall in a home or exhausted up through the roof.

Ventless Gas Fireplace Venting Requirements

Ventless gas fireplaces do not require any form of venting.

These ‘ventless’ or ‘vent-free’ types of gas fireplace burn the gas fuel so cleanly that they’re rated for internal use with no external verting or exhaust requirements.

A ventless gas fireplace will use the oxygen supply within the air in your home. Through use of this type of gas fireplace the oxygen levels within the air can reduce and so it’s commonly recommended not to use a ventless gas fireplace for long periods of time without opening any windows.

One of the main reasons why a ventless gas fireplace doesn’t need venting is that the main by-products are Carbon Dioxide and water vapor, which have been deemed safe by many regulators for indoor use without ventilation. However, this may differ between regions and so always install and use a ventless gas fireplace in line with the manufacturer’s instruction and local codes and regulations.

If a ventless gas fireplace is installed within an existing masonry fireplace then it’s typical that the damper doesn’t need to be open and can be closed when installed, but always confirm with the manufacturer of the fireplace before doing so.

Depending on your area of residence, an external air vent may be required in the room.

Fireplace Vent
A separate air vent located within the room may be required as part of installing a ventless/flueless gas fireplace

Therefore, unlike natural vent and direct vent gas fireplace, ventless gas fireplace do not require any form of external venting in order to work and will simply use the air within a home to work, but depending on your area of residence a separate air vent may be required within the room the ventless gas fireplace is located within.

Waste air from a ventless gas fireplace also doesn’t require any special arrangements such as the use of a chimney of a direct vent to the outside.

Further Reading

Do Gas Fireplaces Have Real Flames And Give Off Heat?

 Are Gas Fireplace Worth Buying?

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