Can A High-Efficiency Furnace Be Vented Through A Chimney?

Rima Chatterjee

Investing in a home furnace is a major decision. It keeps your family warm and cozy in the winter. Nowadays, homeowners choose high-efficiency furnaces, which consume less energy and create fewer exhaust gases. But can they be vented through a chimney? Not always. High-efficiency furnaces produce water vapor and acidic condensate, which could damage chimneys. The ventilation system must be correctly installed. Surprisingly, older furnaces are connected to large masonry flues to remove carbon monoxide fumes. Furnace manufacturers have recommended that even older homes upgrade to safety burners. So, are high-efficiency furnaces and chimneys a good match? Let’s find out!

Can A High-Efficiency Furnace Be Vented through a Chimney

Can a High-Efficiency Furnace Be Vented Through a Chimney?

To make sure your high-efficiency furnace is working properly, you might wonder if it can be vented through your chimney. In order to answer that question, let’s take a closer look at the importance of proper ventilation, and the basics of how chimneys and vents work. In these two sub-sections, I’ll detail everything you need to know about making sure your gas appliances are safely and effectively ventilated.

Understanding Chimneys and Vents in Heating System

Chimneys and vents are essential for your home’s heating and cooling systems to work well. If you’re installing a high-efficiency furnace, can it be vented through a chimney? It depends.

Your chimney needs to be designed for gas appliances, otherwise, it can’t be used due to safety concerns. Plus, it must fulfill the latest code requirements. If your chimney meets these criteria, it can be used to vent the furnace – but an approved liner must be added.

If your chimney isn’t suitable for venting, other options exist such as direct ventilation or sidewall venting. 

Make sure your gas appliances are properly ventilated, otherwise, you don’t want your home to go viral on YouTube!

Importance of Proper Ventilation for Gas Appliances in Heating System

Good ventilation is vital for the safe and efficient running of gas appliances. It helps remove any nasty gases, avoiding carbon monoxide poisoning. Plus, it keeps equipment running well and makes it last longer.

So can a high-efficiency furnace be vented through a chimney? Yes, technically. But it’s not recommended. Chimneys are designed for wood-burning fireplaces and don’t have the right venting needs for high-efficiency furnaces. This means carbon monoxide and other bad gases could stay in your home, risking safety.

You need a direct-vent system or a concentric vent. These have two pipes, one for air intake and the other for exhaust. These pipes go through walls, roofs,s or foundations. Modern venting systems don’t use chimneys, and provide excellent efficiency and safety for high-efficiency furnaces.

Venting Options for High-Efficiency Furnaces

To ensure your high-efficiency furnace is vented properly, you need to consider the best venting option. In this section, we will discuss the different venting choices for high-efficiency furnaces. We will explore the pros and cons of venting through an existing chimney and installing a new ventilation system. Understanding these options will help you determine the safest and most efficient way to vent your furnace to keep your home safe from dangerous gases.

Venting Through an Existing Chimney to the Furnace

Venting a high-efficiency furnace through an existing chimney is an option many homeowners choose. This could involve connecting the vent to the chimney or installing a liner inside. 

  • It’s cost-effective as it removes the need for extra venting.
  • Yet, it’s important to inspect the chimney to ensure there are no obstructions or cracks. 
  • You must make sure the flue size matches your furnace model, plus decide between a single pipe system or a concentric vent system.
  • Also, a fresh air intake system can be added to your HVAC setup. 
  • This can improve energy efficiency and help vent out harmful gases. Different liners are available, too.

In summary, using an existing chimney can be efficient and cost-effective. However, you should consult with a licensed HVAC technician first. Fresh air intake is easy, but don’t forget to ditch the mask and cape!

Installing a New Ventilation System for High-Efficiency Furnace

Are you thinking about installing a new ventilation system for your high-efficiency furnace? Here’s a 5-step guide to make it easier:

  1. Select an option – Consider the efficiency, cost, and regulations before deciding between a direct vent, a power vent, and a natural vent.
  2. Plan the installation – Take into account manufacturer instructions, local codes, and space availability.
  3. Mount the exhaust pipe – Begin by installing the exhaust pipe from the furnace to the outside, following all guidelines and using suitable materials.
  4. Install the intake pipe – Then, install the intake pipe that brings in fresh air from outside. This should comply with regulations and guidelines.
  5. Join it all together – Connect everything, including piping, ductwork, and electrical connections, while ensuring safety.

It might be better to hire a professional if unsure of doing this yourself. Note that altitude can affect the venting options. Consult manufacturers or licensed professionals for advice. Also, be aware that improper installation or inadequate maintenance of the ventilation system can lead to carbon monoxide poisoning. 

The Centers for Disease Control and Prevention (CDC) reports over 20,000 emergency room visits in America each year due to carbon monoxide poisoning. 

Be safe! Don’t try to fit a square peg into a round hole, venting a high-efficiency furnace through a chimney is a big no-no!

The Risks of Venting a High-Efficiency Furnace through a Chimney

To ensure your family’s safety while keeping the furnace efficient, you may choose to vent a high-efficiency furnace through a chimney. But it needs proper installation and maintenance. Venting through the chimney brings two main risks: backdraft and carbon monoxide poisoning, and damage to the chimney and surrounding area. In the following subsections, we will briefly discuss these risks and the solutions to prevent them.

Backdraft and Carbon Monoxide Poisoning in High-Efficiency Furnace

Venting a high-efficiency furnace through a chimney is a risky option. It can cause backdraft and carbon monoxide poisoning

The narrow flue decreases exhaust release speed, resulting in a backflow of hazardous gases. Carbon monoxide is invisible and odorless, making it hard to detect. High levels can be deadly or cause serious health complications.

Alternatives to chimney venting are direct venting or sidewall venting systems. These methods provide proper exhaust flow and reduce the risk of carbon monoxide poisoning.

Get your furnace serviced by a professional technician to ensure safe operation and avoid the threat of carbon monoxide poisoning.

Damage to the Chimney and Surrounding Area of the High-Efficiency Furnace

Venting a high-efficiency furnace through a chimney may seem cost-effective. But, it can damage the chimney and its surroundings. 

  • The furnace’s exhaust gases combine with the creosote and soot in the chimney, forming acidic condensates. These corrode the masonry and steel liner. 
  • Resulting in cracked or crumbled flue tiles. This could lead to smoke, carbon monoxide, or other hazardous substances leaking into your home.
  • Also, venting a furnace through an ill-equipped chimney has more dangers. 
  • Poor combustion air supply, draft problems, and fuel inefficiency. These can put you at greater risk of fire or deadly gases.

Take Fred for example. He installed a high-efficiency furnace without inspection and vented it through his old chimney. After years of neglect, Fred’s flue had a lot of creosote build-up. The heated exhaust reacted with the creosote, causing severe corrosion. He had to replace the entire setup at a great cost.

In short, ignoring chimney damage due to HVAC installation could be disastrous; financially and safety-wise! Venting efficiently is the only way to avoid carbon monoxide poisoning.

Venting a High-Efficiency Furnace Through an Interior Chimney

To vent a high-efficiency furnace through an interior chimney, using a stainless steel flue liner or a PVC vent pipe could be the solution. This section will explain how you can properly vent your furnace through an existing chimney, and the two sub-sections will discuss the benefits of using either a stainless steel flue liner or PVC vent pipe to create a safe, efficient venting system.

Using a Stainless Steel Flue Liner for Venting a High-Efficiency Furnace

Who needs a chimney when you can use a fancy oversized straw to suck out the fumes? Introducing the PVC vent pipe, the high-efficiency furnace’s new best friend!

  • Using a stainless steel flue liner has many benefits. It is durable, flexible, corrosion-resistant, and has a long life span. 
  • Plus, it offers easy maintenance, reliable performance, no crack formation, and is suitable for all fuel types. 
  • It also improves the draft of your chimney system, especially important when venting a high-efficiency furnace.

The history of stainless steel dates back to the early 1900s. Metallurgists were experimenting with different alloys of iron and chromium. The result was “stainless” steel due to its resistance to rust and other forms of corrosion. Initially used in surgical tools and cutlery, it eventually made its way into other industries such as construction and engineering.

In conclusion, stainless steel flue liners bring durability, flexibility, corrosion resistance, easy maintenance, improved draft, and affordability. Plus, its origins date back over a century ago when innovators were searching for stronger metals.

Using a PVC Vent Pipe for High-Efficiency Furnace

Wondering how to vent your high-efficiency furnace through an interior chimney? PVC vent pipes are the perfect solution! Here’s a guide to help get you started.

  1. Measure the height of your chimney. Make sure it’s at least 3 feet higher than the roof peak.
  2. Cut a hole in the side of the chimney that lines up with the furnace vent.
  3. Put a PVC collar into the hole and secure it with silicone adhesive.
  4. Attach a termination cap to the end of the PVC pipe, and insert it into the collar.
  5. Fix support brackets to keep the PVC pipe securely in place as it goes up the chimney.
  6. Connect elbow joints as needed until you reach the top. Finish with another termination cap to keep out debris and critters.

Remember that you may need to change other parts of your furnace system, like air intake or exhaust vents. Always check local codes and regulations first. One great thing about using PVC is that it can increase the efficiency of your furnace. 

My friend installed a PVC venting system in their home. In the end, their furnace was quieter and ran smoother. Plus, with no bulky metal piping in the attic, they were able to create more storage space!

So why vent through an exterior chimney when you can keep your high-efficiency furnace warm and safe inside?

Venting a High-Efficiency Furnace through an Exterior Chimney

To vent your high-efficiency furnace through an exterior chimney, you need to set up the exhaust pipe correctly. This involves installing Draft Induction Fan and Sidewall Venting. Though, you need to be careful when using an exterior chimney to vent your high-efficiency furnace. In the following subsections, we’ll discuss the installation of an exhaust pipe, draft induction fan, and sidewall venting.

Installation of an Exhaust Pipe in High-Efficiency Furnace

Want to install an exhaust pipe for your high-efficiency furnace through an exterior chimney? Follow these five easy steps!

  1. Turn off the furnace and let it cool.
  2. Mark the spot where the pipe will go on the chimney with a pencil.
  3. Use a masonry drill bit to make a hole 1/4 inch larger than the pipe’s diameter.
  4. Put the pipe into the hole and secure it with flashing, screws, or caulk.
  5. Connect the pipe to your furnace.

The chimney should be three feet taller than any other building close by. For best results, get a professional HVAC technician or plumber to help with installation.

Draft Induction Fan and Sidewall Venting for High-Efficiency Furnace

The draft induction fan creates negative pressure in the exhaust. It draws air to support combustion with a fan and uses pressure difference between the inside and outside of the house to move air through the chimney. But it needs electricity to operate.

Sidewall venting, on the other hand, works under natural draft conditions and runs without electricity. But it might not be suitable for all models of high-efficiency furnaces. If you opt for a draft induction fan, make sure to maintain it regularly. 

A faulty fan can lead to decreased efficiency and exposure to harmful gases. Always consult with a professional technician before making decisions about your furnace venting system. Regular maintenance of your ventilation system can save you from dangers, and increase energy efficiency. 

If you want to vent your high-efficiency furnace through a wall, sorry I can’t help you. But I hear the Kool-Aid Man can help break through walls.

Venting a High-Efficiency Furnace Through a Wall

To properly vent a high-efficiency furnace through a wall instead of a chimney, the key is installed. You need to make sure the ventilation pipes are placed and installed correctly to avoid any damage or risk of backdraft. In addition to this, proper management of condensation and the floor drain is important. In this article section, we will briefly describe the two important sub-sections, including the placement and installation of ventilation pipes as well as the proper management of floor drains and condensation for safe and efficient ventilation of your high-efficiency furnace through a wall.

Proper Placement and Installation of Ventilation Pipes

Venting a high-efficiency furnace through a wall requires the right setup. Here’s how to do it:

1.Choose the best spot on the exterior wall, without obstructions.
2.Measure the distance between the furnace and the chosen vent spot.
3.Cut holes in both sides of the wall according to the measurements.
4.Attach the horizontal pipe with screws, without dips or sags.
5.Run vertical piping upward, supporting it with clamps.
6.Fit the pipes securely to handle temperature changes. Check the draft hood for safety.

It’s essential that all joints are sealed properly, to stop air leaks. Safety first! Using this method prevents condensation, updraft issues, and heat loss in cold climates.

If it’s not done correctly, it can cause carbon monoxide gas to accumulate at home and no heating – or even fire accidents. For example, in 2005, in California, improper placements and construction let moisture build up in a chimney with explosive results.

Let’s be careful when installing ventilation pipes – it can save lives!

Floor Drain and Condensation Management

Managing the draining system and condensation is essential for venting a high-efficiency furnace. These furnaces use PVC or ABS piping, which needs proper insulation to stop condensation from forming.

  1. Make sure the drainage design meets local building codes
  2. A ‘P’ trap should be installed under the floor drain to keep sewer gases out. 
  3. Also, check if a backwater valve is necessary for your state code before installing.
  4. Condensation management requires regular checks and cleaning of drainage points. 
  5. High-efficiency furnaces produce more moisture and sediment buildup over time. 
  6. The drainage system must have correct slopes and connections with no dips or sags for water to accumulate.
  7. In the past, there was no knowledge of controlling condensation from high-efficiency furnaces. This caused mold growth and structural decay due to water damage. 

Now, with HVAC systems, dealing with these issues is much simpler. Keep your furnace venting system in good shape or you could have a very unpleasant situation.

Maintaining a High-Efficiency Furnace Venting System

Maintaining your high-efficiency furnace venting system with regular inspections and cleaning, and addressing drafting and combustion issues is paramount. Ensuring that the venting system functions properly is crucial to keep your home safe and your equipment running efficiently. In this section, we’ll discuss the first step towards this goal by performing regular inspections and cleaning, and then we’ll explore the impact of addressing drafting and combustion issues.

Regular Inspections and Cleaning of High-Efficiency Furnaces

To keep your furnace running efficiently, regular inspections and cleaning are essential. Ignoring this can cause critical problems, which could be costly to fix. Blockages can lead to the furnace shutting down, resulting in higher energy usage. 

Blocked vents can also lead to toxic air entering your home, bringing health hazards. Plus, not getting regular inspections and cleaning can void the manufacturer’s warranty.

It’s important to remember that maintenance work must only be done by a professional. Here are a few Tips:

  •  Do not attempt to do it yourself as it’s dangerous. 
  • Avoid an unexpected breakdown on cold days and toxic gases in your home. 
  • Get maintenance services and keep your furnace running smoothly all year long. 

Don’t let draft and combustion issues become like your ex: unpredictable and potentially explosive!

Addressing Drafting and Combustion Issues of High-Efficiency Furnace

Keep your furnace venting system efficient and your sense of humor high! For proper air ventilation, installation, maintenance, and adjustments are key. 

  • Follow manufacturer instructions and local codes when installing. 
  • Clean air filters, exhaust vents, and ductwork annually. 
  • Make sure a qualified technician adjusts combustion issues. 
  • Check for potential hazards like bird nests or debris blocking exhaust pipes or chimneys. 
  • Routinely inspect and clean external vent piping.
  • Upgrade your home with weatherization techniques like storm windows or insulation. 

An insulated home reduces heat loss leading to less demand for heating systems.


As a homeowner, understanding the right venting system for your furnace can be confusing. Many ask if a high-efficiency furnace requires a separate pipe system or if it can be vented through a chimney. It all depends on the type of chimney you have and the furnace’s efficiency rating. Acidic condensate could cause damage. So, it’s recommended to install a new stainless steel flue liner. Interior chimneys may work for venting high-efficiency furnaces with modifications. Try fitting a draft induction fan, ventilation pipes, and cold combustion air intake. Consult an HVAC contractor before making changes to your heating system. Metal-piped systems corrode with acidic condensation. When upgrading or installing a furnace, consider the available chimney and analyze if it will work in the long run. 

About the author

Debarghya Roy: A heating systems author, Passionate about energy efficiency and sustainability, Sharing insights and empowering readers through informative blog articles.