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Vented Vs. Ventless Fireplaces: 7 Key Differences

Vented fireplaces have an external venting system such as a chimney or direct vent. These expel by-products such as carbon monoxide outside your home. These fireplaces burn natural gas, propane, wood, or other fuels, making a realistic flame like a traditional wood-burning fireplace.

Pros of Vented FireplacesCons of Vented Fireplaces
Authentic FlameMore Heat Loss
Less Water VaporComplex Installation
Oxygen Sensor Not RequiredMore Maintenance

Ventless fireplaces (also called vent-free) run without an external vent or chimney. Instead, they’re clean-burning, so emissions such as carbon dioxide are minimal and safer for indoor release. These fireplaces are usually fueled by natural gas or propane, with burners and logs designed to reduce harmful gases.

Pros of Ventless FireplacesCons of Ventless Fireplaces
Energy-EfficientOxygen Sensors Required
Easier InstallationPotential Moisture Buildup
Less MaintenanceLess Authentic Flame

The biggest difference (and concern) with ventless gas fireplaces is the release of H20 and C02 into the home. This not only contributes to condensation (and mold) but reduces the available oxygen in your home. For this reason, some states and cities have banned vent-free gas fireplaces (more on this later).

Let’s take a closer look at the seven key differences between vented and ventless gas fireplaces, followed by my recommendation.

our tv above our fireplace and christmas tree
Our gas fireplace vented by a chimney (if you have a chimney, make sure you keep the damper open while using the fireplace).

1. Appearance

gas fireplace with a blue flame

If you’re shopping for a new gas fireplace, and want to know if you should get a vented or vent-free fireplace, the first thing to consider is the appearance.

Vented fireplaces emulate a real wood-burning fire, often featuring realistic logs, flames, and sometimes even smoke.

The flame in vented fireplaces mimics the random, dancing appearance of a natural wood fire. This can create a warm, cozy ambiance for your living space.

Vented fireplaces are also made in various sizes and styles, including built-in, free-standing, and insert models to fit your decor and space requirements.

Recommended: Fireplace Size vs. Room Size: How To Tell What You Need

On the other hand, ventless fireplaces have a more contemporary look, often featuring clean lines, modern designs, and alternative fuel sources like gel or bioethanol. These fireplaces produce flames without the need for venting, providing a sleek and minimalistic appearance.

Vent-free gas fireplaces, like their vented counterparts, come in various sizes and styles such as wall-mounted, tabletop, and built-in options.

Additionally, ventless fireplaces often feature alternative flame media such as glass beads, stones, or geometric shapes instead of traditional logs, for a more artistic and modern touch.

2. Ventilation

the inside of our fireplace chimney
Inside our gas fireplace’s chimney
Vented FireplacesVentless Fireplaces
Vent TypeDirect Vent or ChimneyRecirculates Indoor Air
HumidityDry AirMore Humid
ByproductsCarbon Monoxide and DioxideWater and Carbon Dioxide

Vented Fireplaces are more traditional and require a chimney or venting system to expel combustion gases and smoke outside. The venting system can either be through a vertical flue or a horizontal one, known as direct venting.

While vented fireplaces provide a realistic flame, they also lose some heat through the venting process, making them less energy-efficient than ventless fireplaces.

Ventless Fireplaces, on the other hand, do not require any external venting, making them easy to install and cost-effective. They operate by burning fuel more efficiently, which significantly reduces the production of harmful combustion byproducts such as carbon monoxide.

Vent-free fireplaces recycle the air within the room, making them highly energy-efficient. However, this recycling process can lead to minor indoor air-quality concerns. The main concerns being moisture and carbon dioxide.

When natural gas (methane) or propane is burned, the primary byproducts are carbon dioxide (CO2), heat, and water vapor (H2O).

In vented fireplaces, much of the water vapor (along with other combustion byproducts) is expelled from the home through the vent or chimney, so it doesn’t notably raise indoor humidity levels.

However, since ventless fireplaces lack this venting mechanism, all the water vapor produced remains inside the room, leading to increased indoor moisture.

While a certain level of indoor humidity can be beneficial, especially in dry climates or during winter, excessive moisture can lead to problems such as:

  • Condensation on windows and walls
  • Increased mold or mildew growth
  • Warping or damage to furnishings, wallpaper, or paint
  • Potential aggravation of respiratory issues or allergies for some individuals
condensation build up inside a window
Condensation buildup on a window can quickly lead to mildew, mold, or other issues.

Without an open window, or another point of access for fresh air, the byproducts of vent-free fireplaces can accumulate in a home.

3. Cost Comparison

installing a vented gas fireplace in a new home
Type of CostVented FireplacesVentless Fireplaces
Installation$2,000 to $5,000$1,000 to $2,000
Fuel$0.20 to $0.60 per hour$0.20 to $0.60 per hour
Maintenance$100 to 150 per year$50 to $100 per year

Installation costs for vented fireplaces can be higher as they require a proper venting system, usually a chimney or a direct vent system. This can be pricey, especially if your home doesn’t have a preexisting chimney.

On the other hand, ventless fireplaces have lower installation costs since they don’t require venting. However, you may need to invest in additional safety features, such as an oxygen depletion sensor.

Fuel efficiency plays a big role in the ongoing costs of your fireplace. Vented fireplaces lose some heat through the venting system, making them less efficient and resulting in higher fuel costs. Vent-free fireplaces are more efficient since they don’t lose heat through a vent. This means you’ll spend less on fuel, which can save you money in the long run.

Keep in mind that natural gas is typically cheaper than propane (closer to $0.60 per hour to run).

Maintenance is another crucial aspect when it comes to cost comparison. Maintenance costs for both vented and ventless fireplaces can vary, but some general rules apply:

  • Vented fireplaces usually require regular chimney cleaning to prevent blockages and ensure safety. This can incur additional costs.
  • Ventless fireplaces need regular cleaning and inspection of the burners, ignition systems, and safety features. However, they are generally easier to maintain than vented fireplaces.

4. Heat Comparison

gas fireplace with a blue flame

Vented fireplaces typically have lower heat output as compared to ventless fireplaces (average of 20,000 to 25,000 BTUs). This is because vented fireplaces lose some of the heat through the venting system—exhausting it outside. For example, a gas-vented fireplace may have an efficiency rating of around 60-80%.

On the other hand, while ventless fireplaces have a similar maximum heat (20,000 to 30,000 BTUs), they are designed to have a higher heating efficiency.

Since no venting is required for these fireplaces, the heat produced remains within your living space without any loss. As a result, ventless fireplaces generally have a heating efficiency rating of around 90-99%. This makes them quite effective at raising the room temperature.

However, the improved heat output of ventless fireplaces does come with a slight trade-off: humidity.

Ventless fireplaces tend to produce more humidity within the living space, which can make the room feel damp or muggy. This can lead to future issues with condensation and mold.

In contrast, vented fireplaces remove the moisture along with the exhaust, resulting in a drier heat.

To summarize the key points:

  • Vented fireplaces have a lower heat output due to heat loss through the venting system.
  • Ventless fireplaces are more heat efficient, with minimal heat loss.
  • Vented fireplaces provide drier heat, while ventless fireplaces produce more humidity in the room.

Recommended: Why is Fire Blue (& Is It Hotter)? Answered

5. Ease of Installation

taking off the glass door to a gas fireplace

Vented fireplaces require a more complex installation process, as they need a proper ventilation system to operate safely. This often involves the construction of a chimney or the installation of specialized venting pipes. In addition, you may need to obtain building permits and ensure that the installation meets local building codes.

Ventless fireplaces are generally simpler to install. Since they don’t produce harmful emissions, there is no need for a ventilation system. This means you can install a ventless fireplace in a variety of locations without worrying about venting requirements. Some ventless fireplaces are even designed to be portable, making the installation process as easy as placing the unit in your desired location.

However, remember that ventless fireplaces may have restrictions based on the type of fuel they use. For example:

  • Gas ventless fireplaces often require a connection to your home’s natural gas line or propane supply. This may involve hiring a professional to make the connection, adding to the installation costs.
  • Gel and ethanol ventless fireplaces do not require any additional connections, as they use fuel cans or cartridges. This makes their installation process relatively easy and quick.

In summary, ventless fireplaces generally offer a simpler and more flexible installation process compared to vented fireplaces. However, you should still take factors like fuel type and potential restrictions into account when making your decision.

6. Safety Concerns & Precautions

closing the doors on a fireplace

With vented fireplaces, you’ll enjoy the added safety of venting harmful byproducts, such as carbon monoxide, outside your home.

However, this doesn’t mean they’re without risks. It’s crucial to have regular chimney inspections and cleanings to avoid creosote buildup (recommended once per year), which can lead to chimney fires.

“Fireplaces, Chimneys, Flues and Venting Systems need to be inspected at least once a year for freedom from deposits, soundness, and correct clearances. Maintenance, Repairs and Cleaning shall be done if necessary.”

National Fire Protection Association

Additionally, make sure to install carbon monoxide detectors near your fireplace and throughout your home.

installing a carbon monoxide sensor
The Inter­national Association of Certified Home Inspectors (InterNACHI) has recommendations on where to put carbon monoxide sensors (more on this below).

On the other hand, ventless fireplaces have a different set of safety concerns. Since they don’t have a venting system, they release combustion gases and moisture directly into your living space. As a result, high-quality ventless fireplaces come equipped with an Oxygen Depletion Sensor (ODS) that shuts off the gas supply if oxygen levels in the room dip too low.

“Massachusetts, California, and a number of other states in the U.S., as well as Canada and other countries, have outlawed ventless gas fireplaces due to the aforementioned safety concerns. Many individual municipalities, too, have outlawed these appliances in states where they are otherwise legal. “

Nick Gromicko, CMI, Inter­national Association of Certified Home Inspectors (InterNACHI)

Here are some basic guidelines when using vent-free fireplaces:

  • Only use the approved fuel for your fireplace – typically, a natural gas line or propane.
  • Avoid using the fireplace for long periods or as a primary heat source.
  • Make sure the room has adequate ventilation, such as opening a window, especially during use.
  • Keep flammable objects, like furniture and curtains, at a safe distance (at least 3 feet)
  • Have your ventless fireplace regularly inspected and serviced by a professional.
opening a window
It’s recommended to open a window when using a ventless gas fireplace

According to the InterNACHI website, they also recommend avoiding using ventless gas fireplaces in a room where people are sleeping.

To learn more about carbon monoxide, including where to place the sensors, see this guide by the Inter­national Association of Certified Home Inspectors (InterNACHI).

7. Legal Use

maintenance of a vented gas fireplace

In many locations, ventless fireplaces face restrictions due to potential health and safety concerns. For example, some states in the US (such as California and Massachusetts) and provinces in Canada forbid the installation of ventless fireplaces, while others require specific safety features or have strict guidelines regarding their use.

Keep in mind, that even if your state allows vent-free fireplaces, it also comes down to your local laws.

To avoid any legal and safety troubles, it’s best to consult with a professional during the planning stages. They will guide you on the most suitable option and make sure it meets all requirements.

Vented fireplaces, on the other hand, are generally accepted in most regions since they expel emissions outside, minimizing the potential for indoor air quality issues. However, some areas may still have specific regulations, such as requirements for chimney heights or the type of fuel used.

Always check your local codes to ensure your vented fireplace complies with the stipulated regulations.

Additionally, you may need a permit for installing or replacing a fireplace in your home. This step is essential to ensure your installation adheres to local safety standards and guidelines. Not following these regulations may result in fines, penalties, or even the removal of your fireplace.

At the end of the day, each fireplace has different regulations and requirements, and they vary from state to state or even city to city. Do your research and ensure that the fireplace you choose complies with your local laws.

My Recommendation: Vented Gas Fireplace

Our fireplace in our living room
Our vented gas fireplace (via chimney) with our dog Banjo on the couch

For our home, our indoor gas fireplace is vented through a chimney. If you also have a chimney, remember to open the damper to allow for the proper ventilation of gasses.

On the other hand, if your gas fireplace has a horizontal, or direct vent, it likely won’t have a damper or intake switch as this type of fireplace doesn’t use inside air for combustion. Instead, direct vent fireplaces have a sealed glass front and use outside air for both intake and outtake.

Here’s why I recommend vented gas fireplaces as the best choice over ventless:

First, vented gas fireplaces offer better indoor air quality as they expel combustion gases directly outside, reducing exposure to harmful pollutants. This helps maintain a healthy environment for you and your family.

Second, vented gas fireplaces provide a more authentic fire experience. They produce taller, more natural-looking flames, resembling a traditional wood-burning fireplace. This can create a cozy and inviting atmosphere in your living space.

Efficiency is another factor that sets vented gas fireplaces apart. While vent-free gas fireplaces may have higher efficiency ratings, vented gas fireplaces can still provide considerable energy savings.

With the right combination of a well-insulated home and proper use of your thermostat, you can effectively lower your heating costs.

Vented Gas Fireplace Advantages:

  • Better indoor air quality
  • Authentic fire experience
  • Lower heating costs with proper usage

Don’t forget that vented gas fireplaces have a wider range of decorative options available. From traditional to contemporary, you can find a design that complements your home’s decor.

With different gas log sets, decorative media, and finishes to choose from, you can create a truly unique and personalized fireplace.