Furnace Exhaust Pipe Guide

Furnace Exhaust Pipe Guide: How to Find the Right One

On most occasions, the weather condition becomes too chilly, making homes uncomfortable.

At this point, all you require is a furnace to ensure that your home remains warm regardless of the changes in the weather condition. However, there are various things that one needs to understand regarding this appliance to make it easy to use and maintain.

Also known as exhaust flues, many people wonder how it works to keep the home warm. Continue perusing through this furnace exhaust pipe guide for more crucial info! Note that it’s vital always to keep your furnace active to ensure that the appliance keeps you warm during cold weather conditions, especially during winter.

How Does the Furnace Exhaust Pipe Work?

According to the analysis done by the manufacturers of the furnace exhaust pipe, the appliance burns the natural gas found in your home to ensure that the condition remains warm.

Note that the byproduct of the entire process is carbon monoxide which is highly toxic. Following its toxicity nature, it is necessary to eliminate it from the home’s surroundings to the outside for safety.

Does this make sense to you? Don’t worry! Let’s break it down in a simple way! The furnace burns natural gas through a process known as combustion, thus developing heat among other toxic byproducts such as carbon monoxide.

This is precisely where the furnace exhaust flue becomes very important, ensuring that carbon monoxide is eliminated safely.

Inside the furnace, there is a special type of equipment known as a damper/ natural draft. This equipment is meant to regulate the air pressure inside the furnace and outside the home.

The natural draft then makes it easy to create a draft that helps pull the toxic gases via the pipe towards the outer part of the house. This makes the house remain safe from poisonous gasses and remain warm.

Natural Draft/Damper

Furnace Exhaust Pipe

Most furnace systems available on the market uses natural draft for their functioning. This is referred to as the ability of flue gasses to get their way out by rising through the furnace exhaust pipe.

The natural draft found in the exhaust system is established due to pressure differences in the air outside the home and that found inside the furnace.

Besides, the air found inside the furnace system is usually hotter than the outside air due to the ongoing combustion process. This is an indication that the air from outside the house has lower pressure. The pressure difference enables the exhaust fumes to be pushed out of the furnace system through the exhaust pipe.

Note that if the pressure difference is minimal, the chances of pushing the fumes out of the house via the exhaust pipe becomes minimal. In other cases, too many elbows in the pipe with horizontal sections and inadequately wide pipes can cause struggle when the fumes exit the furnace system.

Draft Inducers

It is said that older furnaces use natural drafts to function while the modern type features draft inducers to operate exemplarily. It is critical to understand that the furnaces using natural drafts are relatively cheap than those utilizing draft inducers. What is the main reason behind the difference in prices between the two?

The main factor impacting the appliance prices is that the speed of the draft is not enough to efficiently eliminate the exhaust fumes from the furnace system.

The type of furnace that lacks draft inducers is costly when it comes to maintenance matters. This is due to their low levels of efficiency, thus making most homeowners go for the furnaces with draft inducers.

What is a draft inducer? This is a special type of highly-powered fan based near the heat exchange inside the furnace system.

This helps to ensure efficiency in exiting fumes from the system. Also, the equipment helps ensure no toxic fumes remain inside the furnace system, especially in the combustion chamber where the entire process occurs.

Where Should The Exhaust Flue Go?

This is another crucial area where most people wonder what to do to ensure that their homes are safe and the environment in general. The exhaust flue should either go on top of the roof or out of the side of the house. Also, the answer to where the exhaust pipe should depend on the type of furnace system you acquire.

There are two types of furnace systems in the market. Let’s get to know each of the two types in detail.

High-Efficiency Furnace

This furnace system has an energy efficiency level of 90% and above. In addition, the furnace comes with an exhaust pipe that is explicitly meant to stick by the side of your house.

The horizontal exhaust pipe drains the liquid byproducts generated during the combustion process, ensuring that the house remains free from toxic substances.

Standard-Efficiency Furnace

This furnace system has an energy efficiency level that is below 90%. The system comes with an exhaust pipe that goes up through the roof of your house after installation.

Note that the standard-efficiency furnace generates byproducts in gasses that are then eliminated outside through the pipe. In some cases, the gasses float up through the pipe and outside the house.

The Installation Process of The Furnace Exhaust Pipe

Furnace Exhaust Pipe

The installation of the furnace exhaust pipe significantly impacts the functioning and well-being of the furnace exhaust system. This means that you should be extremely keen while handling this significant step. The installation process includes the following:

Take Relevant Measurements

At this point, you should measure the distance between the furnace and your chimney. There should already be a connection between the two on most occasions, thus making it easy to identify the measurements.

Acquire Supplies

You should purchase single-wall galvanized pipe together with elbows. Don’t forget to add1-inch galvanized hanger strap to make the installation process easy.

However, ensure that all the supplies that you acquire match the size of the furnace exhaust pipe. Note that this is what will make the flue pipe complete. Also, ensure you get a pipe crimper in case you need to cut the flue to fit.

Make the Furnace Exhaust Flue

Beginning at the furnace, install the flue pipe towards the chimney connection. This is the point at which the connection begins. Perfectly connect the pieces of the galvanized pipe by inserting the crimped end of each piece into the end that is non-crimped.

Ensure that the pieces are tightly held together by at least four sheet metal screws. Cut short the exhaust pipe to fit its position and crimp the end of the piece that you cat.

Secure the Furnace Exhaust Pipe

With the use of a 1-inch galvanized hanger strap, hand the exhaust pipe from the joists of the ceiling Screw one end up on the hanger strap towards the ceiling joist and loop it around the exhaust pipe. Position the other end of the strap to the opposite end of the ceiling joist to the exact position you intend to fasten it.

Cut off any strap that seems excess and screw its end to the ceiling joist. The exhaust pipe should sit at the middle of the hanger, appearing like the letter U.

What You Need to Know About Exhaust Furnace Pipe Replacement.

Typically, you can reach a point and get it vital to carry out furnace replacement. Even though this will take some time before you think about it, it is indispensable to understand various things for your furnace replacement. Several furnace vent replacement options are available to cater to your exhaust furnace pipe needs.

Remember that it is crucial to understand what you are doing to ensure that your family is not in danger imposed by carbon monoxide.

Analysis has revealed that gas furnaces are the most reliable and efficient home heating options during cold seasons. However, they do not generate combustion exhaust fumes that incorporate carbon monoxide gas.

Even though the HVAC contractor is said to be the principal advisor at this point, it is also critical to consider the analysis report done in the industry. Below are the most recommended hacks meant to make your work easy during the replacement of your furnace system.

Our Top Recommended Furnace Vent Replacement Options.

Below are some of the furnace vent replacement options that we highly recommend. This list was compiled based on the durability and efficiency of these products; therefore, you will be confident that they will last a long time.

Concentric Venting

This mode of furnace vent replacement features a couple of vent pipes and comes in different types, as outlined below.

Diversitech CVENT-2 Concentric Vent

Diversitech CVENT-2 Concentric Vent

This is a 2-inch concentric vent that makes it easier to two pipe installation in high-efficiency furnaces. The vent measures 7.75 by 34.75 by 6.75, thus making it perfect for your home furnace needs.


  • The Diversitech CVENT-2 comes with a simple design that makes it easy to hide the exhaust and the intake for a perfect finish.
  • The vent has a flexible design that can be either applied horizontally or vertically.


  • Even though this vent is of high quality, it is relatively expensive.

Rheem SP20245 Concentric Vent

Rheem SP20245 Concentric Vent

This is a comprehensive type of furnace vent that comes with numerous benefits when used efficiently.


  • It can be used both vertically and horizontally.
  • It is affordable.


  • It is not easily found

Sidewall Venting

This mode of venting uses either one or two-pipe system to operate effectively. It comes in different types, as outlined below.

Tjernlund SS1 Oil Side Wall Vent

Tjernlund SS1 Oil Side Wall Vent

This sidewall system vent comes with a UC1 Universal Control to enhance reliability, safety and elevates performance. However, it is designed for oil-fired heating equipment as well as a deluxe gas vent system.


  • It can be easily installed without clearance to combustible materials
  • It is made of stainless steel in critical areas to prevent rusting
  • It has been wired safely to enhance simple interlock


  • It is costly

Vent HoodVH1-6 Vent

Vent HoodVH1-6 Vent

This vent is mainly meant to terminate most horizontal vented appliances.


  • It is flexible enough for ease of installation.
  • It is affordable.


  • It is not easily found.


Question: Should a Furnace Exhaust Pipe be Covered?

Answer: Most high-efficiency gas furnaces come with plastic vent pipes that are extended to the outdoors to eliminate toxic gases from the combustion chamber and introduce fresh air into the system from the surrounding.

If you do not take responsibility for protecting the pipes, you are at a considerable risk of getting furnace-related problems.

Question: What Type of Pipe is Used for a Furnace Exhaust?

Answer: Note that furnaces produce hot combustion exhaust gasses, therefore, require metal exhaust pipes to withstand the temperature of the byproducts produced. However, there are modern high-efficiency condensing furnaces that produce cooler gasses, thus require plastic pipe exhausts.

Question: What is the Maximum Length of a Furnace Exhaust Pipe?

Answer: Analysis has revealed that the maximum distance you can run a vertical furnace exhaust vent is fifteen feet. On the contrary, if there is a forced air inlet located about ten feet from the exhaust vent, the exhaust gas ventilation tunnel should be placed about three feet above it.

Question: Why Does the Furnace Exhaust Stink?

Answer: This is a normal thing for the exhaust system. This happens when the furnace exhaust pipe is blowing back via an open window or door.
Note that it is normal to smell gas in the exhaust pipe from the HVAC system. This is said to be the way to get rid of fuel or gas that may not have been completely used in the furnace system.

Question: Can Snow Block the Furnace Vent?

Answer: It is advised to keep the furnace vents clear and away from the snow. This is because the vents can be entirely blocked by snow or ice.

Also, if you do not have proper ventilation, you increase the chances of carbon monoxide building up inside your home. Remember that when the vents are entirely blocked, they affect energy efficiency.

Bottom Line

The furnace system is an exceptional appliance to have at home, especially during cold seasons. However, there are many things concerning the appliance that one needs to understand to use it effectively and enhance its well-being.

The good news is that this guide will help you through every step of the way. Let us know how the products recommended work for you. We would love to hear it.

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