Does A Gas Fireplace Need A Chimney? (B-vent, Direct Vent, Ventless)

When you are planning to install a gas fireplace in your home, one question that comes to mind is; does a gas fireplace needs a chimney?

Depending on their type, many gas fireplaces do not need a chimney. Direct vent gas fireplaces can be installed and used safely without a chimney as you can vent them outside directly. On the other hand, ventless gas fireplaces do not need to be vented outside, so they do not need a chimney. However, B-vent gas fireplaces will need a traditional chimney to be vented.

If you already have an existing chimney, you may want to know if you can utilize that for venting your gas fireplace. Let’s look at how the gas fireplaces work and how to install and use them safely. In this detailed article, read on to find out more about gas fireplaces and their chimney requirements.

A house with a chimney

What are the different types of gas fireplaces?

Three main types of gas fireplaces have different features, operating efficiencies, and installation methods. Let’s briefly look at their essential characteristics.

1. B-vent gas fireplaces

These are aesthetically pleasing fireplaces with less heating efficiency than direct-vent fireplaces. They need to be vertically vented using B-vent pipes for exhaust, hence the name.

2. Direct-vent gas fireplaces

These fireplaces offer better aesthetics, heating efficiency, and more freedom in choosing a place of installation. They are an efficient way of providing supplemental heat because of their heat circulating feature.

3. Ventless gas fireplaces

The ventless fireplaces offer the ultimate installation flexibility compared to b-vent and direct-vent fireplaces. They also have the best heating efficiency among these three fireplace types.

Do gas fireplaces need to be vented outside?

Local building codes and regulations require vented gas fireplaces to vent outside using a chimney or a vent. B-vent fireplaces require venting through the chimney, whereas direct-vent gas fireplaces need a dual vent pipe to vent out the exhaust. However, ventless gas fireplaces do not need to be vented outside, but in some areas, local building code requirements may be different, and you may need to have an external vent in the room where you are planning to use a ventless gas fireplace.

Three main types of gas fireplaces with different venting requirements are currently available to homeowners. Let’s look at their individual requirements in some detail:

Does a B-vent gas fireplace need a chimney?

A B-vent gas fireplace needs a suitable chimney to eliminate harmful exhaust fumes.

These gas fireplaces work by drawing air from outside through a small hole in the back of the unit and then circulating it through the fire chamber. It is an ideal fireplace for homes with an existing chimney, as they can be vented directly through it. 

B-vent fireplaces rely on a natural draft system to exhaust the combustion gases outside the house using a particular pipe system. A chimney provides the best place to run the pipe through and terminate above the roof outside the home. B-vent pipes follow the same standards as that of a masonry chimney. Also, ensure that the chimney damper is open when this fireplace is under use. 

Although the B-vent pipe system isn’t complicated, you must hire a professional to ensure that all building codes and installation safety measures are followed appropriately.

Does a direct vent fireplace need a chimney?

Direct vent fireplaces require a direct vent instead of a chimney to vent the combustion exhaust. Instead, they use two pipes to draw in air from outside and expel exhaust out of the home. It makes them a safe and efficient option for heating your home. You can easily vent direct-vent fireplaces through the external wall or the roof according to convenience. 

Not needing a chimney allows for more freedom of installation for these fireplaces. A direct-vent fireplace can be installed in many locations within the home, whereas a b-vent fireplace can only be installed where the chimney is located. 

Direct-vent fireplaces are the safest option as they have a glass barrier and don’t use the room’s air for combustion, so there is no oxygen depletion when operating. It’s important to remember that although direct-vent fireplaces don’t require a chimney for venting, you must ensure that their installation is according to the local building codes to ensure safety.

Does a ventless fireplace need a chimney?

Ventless gas fireplaces are ventless! You do not require a chimney or any other form of venting as these fireplaces burn the fuel completely and produce significantly fewer combustion by-products. They exhaust back in the room air, so they come with oxygen level monitors for safety.

Ventless gas fireplaces are fueled by either natural gas or propane. A small pipe runs from the gas line to the fireplace, providing a steady fuel supply. Because of no venting requirements, they can be placed anywhere in the home where heat is needed. However, some areas have restrictions on ventless fireplaces, and you may require an external vent for safety purposes. 

Check your local laws for using ventless fireplaces before you buy a fireplace and install the unit by following all safety measures and requirements.

Can You install a gas fireplace without a chimney?

If you plan to have a gas fireplace but don’t have a chimney, then your best option is to install a direct-vent or ventless fireplace.

A direct-vent gas fireplace is an excellent option for those who want an ambiance of a fireplace without any hassle. These fireplaces are very efficient, providing more opportunities for installations as they can be terminated through the outside wall or up the roof to be used in any room in your home. Plus, they don’t use inside air for combustion, so they don’t deplete oxygen levels while the harmful emissions are exhausted outside the home. So you can feel safe about using one in your home.

Similarly, a ventless gas fireplace is an easier option if you don’t have a chimney and don’t want to vent the gas fireplace through the exterior wall for any reason. It is also an energy-efficient and eco-friendly way to warm your home.

What kind of chimney does a gas fireplace need?

You don’t always need a chimney to vent a gas fireplace. However, if you choose a b-vent fireplace or if you want to run a direct-vent fireplace through it, check the following for an efficiently running gas fireplace:

  • Ensure that your fireplace and chimney are big enough according to the size of your unit. Also, check if your model fits easily into the fireplace dimension.
  • Remember to clean the chimney before installing the fireplace properly so it doesn’t hinder the performance.
  • Schedule an annual maintenance check to ensure there aren’t any issues with the chimney that can affect the smooth running of the fireplace.

How do you vent a gas fireplace?

A vented gas fireplace can be vented in two ways: 

Venting through a chimney

The b-vent gas fireplaces need a chimney to vent outside. These gas fireplaces don’t have a sealed system, so they take air from inside into their chamber for combustion. They have a single exhaust pipe that goes through the chimney and up through the roof to get the exhaust fumes outside the home. B-vent fireplaces can only vent vertically as they rely on the natural mechanism of hot combustion gases to rise up and out through the roof chimney.

Venting without a chimney

Direct-vent gas fireplaces can be vented without a chimney. There are three options when venting these fireplaces. Let’s look at them in some detail.

Horizontal venting

Horizontal or through-the-wall venting is easier and more efficient as it doesn’t depend on the natural draft of a chimney. It involves a vent pipe from the back of the fireplace running slightly upward and then out of the exterior wall, ending with a termination cap.

Vertical venting

If you want to install a direct-vent fireplace and there isn’t an exterior wall to vent out the fireplace, venting through the roof or vertical venting is recommended. It gives freedom to place the fireplace anywhere in the room. However, it is a costly option and requires more work. It is also risky as water can leak through the roof if the vent pipe is not installed correctly.

Power venting

This technology facilitates the venting by pulling the air mechanically through the venting pipes. It allows maximum flexibility to install the fireplace anywhere without compromising its efficiency and venting ability.

What is the best venting option for gas fireplaces?

It depends on the availability of an existing chimney, and your heating needs to decide which option will best suit your project. For example, if you are more inclined to install a b-vent gas fireplace, your only option is to vent through the chimney. Consider the reason for installing a gas fireplace, and then go for the venting option that is most convenient and will give you an efficiently operating fireplace according to your specific needs.

Can you use an existing chimney for venting a direct-vent fireplace?

When venting a direct-vent gas fireplace, you might have two options. Either you have an existing chimney, or you don’t. That’s what you can do in these situations:

  • If you have an existing chimney that doesn’t need any repair work and is in fine working condition, you can run the vent pipe directly through the chimney and terminate up above the roof.
  • If you don’t have a chimney, vent outside through the exterior wall. If it isn’t possible, then go venting through the roof.

Choose one venting option from above that is more feasible according to the situation.

Frequently Asked Questions

Can two gas fireplaces share the same chimney?

Any gas-fired appliance must have a separate flue to lead the combustion gases out of the building. Sharing a single chimney among two different appliances may pose a fire hazard. Also, a gas leak or fire risk increases if these two appliances are located on separate floors. Every local building authority has strict codes for shared flues, so check them before you decide on sharing the same chimney for any gas appliance.

Can a vent-free gas fireplace be vented?

Vent-free or ventless gas fireplaces don’t have the provision to convert them to a vented fireplace. If you are unhappy with your vent-free gas fireplace, or you want to have a vented fireplace in its place, you can just get rid of your old vent-free fireplace and install a vented gas fireplace instead.

Can you vent a gas fireplace through the floor?

With a power venting system, you can easily route a direct-vent fireplace through the floor without compromising performance. Power venting has no restrictions on having a rise; the vent can go up, down, zigzag, or even under the floor if the situation requires them to do so. The vent can then terminate outside through an exterior sidewall.

How much is the cost to install a gas fireplace without a chimney?

Installing a gas fireplace without a chimney can be cheaper and easier than installing one with a vent (if you don’t have an existing chimney). Ventless fireplaces are the cheapest to install as they don’t require labor-intensive work. You can expect to spend $800 to $2,600 on a ventless fireplace. On the other hand, a direct-vent gas fireplace can cost you from $1,700 to $12,500.

Do you need a professional to install gas fireplaces?

You can do it yourself if you have expertise in installing gas fireplaces. However, it is better to hire a professional who can advise you on building laws and codes so you don’t have any problems in the future.


If you’re thinking of adding a gas fireplace to your home, you have two main types: vented and ventless. You might not always need a chimney for vented gas fireplaces, depending o their venting needs. Also, each type of gas fireplace, i.e., b-vent, direct-vent, or ventless, has specific advantages and drawbacks, so it’s essential to do thorough research before deciding on a suitable gas fireplace for your home.

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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