do you need a chimney for a gas furnace

Do you need a chimney for a gas furnace? Apparently, it seems that everyone should have some sort of ventilation option with gas furnaces.

But, is it necessary to go with a chimney?

Chimneys may appear antiquated in this day and age of cutting-edge HVAC systems, but they serve an important purpose.

Getting down to the nitty-gritty of fireplace flues and gas stoves will help highlight the importance of chimneys.

But, when do you really need to consider using a chimney?

You need a chimney if your gas furnace is in the basement, you want to improve condensation, you have a specific type of furnace, or a building code requires it.  

Understanding More about the Role of a Gas Furnace

info about the role of a gas furnace

In many residential and commercial buildings, the gas furnace is the primary heat source.

These furnaces are so popular because of many reasons, such as:

  • Minimal operating cost
  • Energy efficiency
  • Less environmental impact

However, adequate venting must accompany the installation to guarantee the gas furnace’s safe and effective operation.

Chimneys are one of the most typical methods of venting indoor air.

But, to confirm if you need a chimney, you have to consider the type of furnace you have and the problems you face for not using a chimney properly. 

Do You Need a Chimney for a Gas Furnace?

gas furnace and chimney necessity

Yes, it is a good idea because it ensures proper venting and proper venting has various benefits.

Here are a few reasons why you may want to install a chimney for your gas furnace:

You Need a Chimney to Enhance Safety

The use of a chimney in conjunction with a gas furnace dramatically improves safety by venting the carbon monoxide and other combustion byproducts outside of the home.

This prevents carbon monoxide poisoning and other health problems caused by a buildup of toxic gases inside the structure.

Proper chimney maintenance also reduces the likelihood of blockages, which can lead to a buildup of gases and negatively impact interior air quality.

A well-functioning chimney aids in the safe and effective operation of the furnace by regulating draft and airflow.

Incomplete combustion is less likely to occur as a result.

Fact: A gas furnace with a properly installed chimney helps to reduce the risk of exposure to dangerous combustion byproducts. 

You Need a Chimney to Enhance Efficiency

you need a chimney to enhance efficiency

Chimneys are used for venting the exhaust gases produced by gas furnaces safely outside of the structure, which helps to greater efficiency.

This keeps the gases from leaking back into the furnace, where they could cause significant heat loss and compromise the unit’s efficiency.

A well-built and regularly serviced chimney will allow the furnace to burn fuel more cleanly and produce more heat.

In addition, improved venting makes cleaner combustion possible, reducing the risk of inefficient byproducts. 

You Need a Chimney to Improve Condensation Control

The use of a chimney with your gas furnace is essential for preventing the buildup of moisture inside the ventilation system.

If condensation were to form inside the system, proper venting would assist in keeping the temperature and airflow at just the appropriate levels to keep it from building up.

chimney for condensation control

Untreated condensation can cause heat exchangers and vent pipes in a furnace to corrode and fail before their time.

Fact: A properly operating chimney protects the gas furnace from breakdowns and extends its useful life by regulating exhaust gas temperatures and avoiding condensation. 

You Need a Chimney to Comply with Building Code

Having a chimney for your gas furnace is generally necessary to meet local building standards.

In order to guarantee the safety and efficiency of homes, governments at both the state and federal levels establish these building regulations.

Particularly for gas furnaces, they typically require the installation of a chimney or other means of venting the furnace’s exhaust.

Failure to comply may result in fines and risk your health and safety, so it is important to do so. 

Choosing the Right Type of Chimney for Your Gas Furnace

optimal chimney selection for gas furnace

When you have decided to use a chimney for your gas furnace, you must take your time and consider some factors first.

Using the right type of chimney is crucial, and many factors play a role, such as:

  • The type of furnace
  • The building’s construction
  • The local restrictions

Here is a bit about the different types of chimneys you can choose for your gas furnace. For instance: 

Conventional Chimney Made of Masonry

conventional chimney made of masonry

Masonry chimneys can withstand the high temperatures produced by combustion because they are made of brick, stone, or concrete blocks.

They are sturdy and long-lasting, but only if you give them the care they deserve on a regular basis. 

Chimneys Made of Corrosion-Resistant Metals

These chimneys are made using materials like stainless steel or aluminum.

They are usually much more convenient to set up than their brick counterparts due to their portability and simplicity of construction.

They are more cost-effective in the long run and require less upkeep, thanks to their insulation. 

Direct Vent Systems

direct vent systems

These systems, also known as sealed combustion systems, vent combustion air and exhaust gases straight outside through a wall or roof vent.

This system is convenient because it does not need a conventional chimney to function. 

Situations When a Gas Furnace Needs a Chimney

A gas furnace requires a chimney for venting in a few different scenarios: 

When You Use Specific Furnaces

when you use specific furnaces

 All furnaces, but especially those with lower AFUE ratings and higher AFUE ratings require adequate ventilation for safe and efficient operation.

A chimney is an integral part of any such furnace, as it facilitates exhaust gas safe and effective release.

Non-condensing gas furnaces produce high-temperature exhaust gases and, if not properly vented, can damage both the furnace and the structure.

Condensing gas furnaces function in a similar manner, though they produce exhaust gases at a lower temperature because of their high efficiency.

The accumulation of moisture can cause corrosion and structural damage to the appliance and the building, so a chimney is essential for proper ventilation. 

When You Install in a Certain Place

when you install in a certain place

The ventilation requirements of a furnace are highly dependent on its placement.

Installing a gas furnace in a basement or other enclosed space with no windows or other means of natural ventilation may require constructing a chimney.

The chimney ensures safe and effective removal of combustion byproducts such as toxic gases.

This makes the installation of a chimney an essential part of the heating system for any such interior installations.

Fact: If a building already has a chimney suitable for venting a gas furnace, using that chimney rather than installing a new one may be the most cost-effective option. 

Do You Need a Chimney Liner for a Gas Furnace?

gas furnace chimney liner need

For reasons of both safety and efficiency, as well as code compliance, gas furnaces require adequate venting.

Chimneys are a common method of venting, but a chimney liner is often recommended to improve efficiency and prevent accidents.

Factors to Consider When Choosing a Chimney Liner

There are a number of things to think about when choosing a chimney liner for your gas furnace, including: 

Consider the Type of Furnace

As mentioned already, condensing and non-condensing furnaces have different venting needs and may call for different liner materials.

For non-condensing furnaces with greater exhaust gas temperatures, a stainless steel liner may be required.

However, aluminum liners may be more appropriate for condensing furnaces operating at lower temperatures. 

Consider the Size

consider the size

The liner’s measurements must agree with those of the chimney in order to provide adequate ventilation for the gas furnace.

The liner must also be flexible enough to follow any curves or offsets in the chimney’s brickwork. 

Consider the Material

Chimney liner materials should resist corrosion and high heat.

Liners made of stainless steel are highly recommended because of their longevity and resistance to corrosion from combustion byproducts.

consider the material

You must check your local building codes and regulations to ensure the chimney liner you choose is up to code regarding safety and performance.

Fact: Chimney venting is necessary because of local or national regulations; this is especially true when installing a gas furnace in an older home with an existing chimney. 


Do you need a chimney for a gas furnace? Turns out, you do.

Without proper ventilation, your gas furnace may no longer be as effective and efficient as it should be.

And a chimney ensures proper venting, which is why you should consider getting one.

But, do not ignore certain factors, such as the type of furnace, its location, and the building code when selecting the best chimney for your gas furnace.