What is a Direct Vent Chimney?


Trying to figure out what kind of pipe you need to install for your fireplace, stove, or any other venting hearth appliance can be a daunting task. 

The pipe needs to be a specific size in order to exhaust properly. You can’t mix different brands or metals or sizes. Plus, you need to make sure the pipe is fit for the type of fuel you’ll use.

There are plenty of other rules like these that contribute to the difficulty in buying chimney pipes. Today’s post will help you become a bit more familiar with chimney pipes. 


Before we get started, you’ll need to begin by consulting the owner’s manual for your appliance. Different fireplaces and stoves will have varying requirements.

These requirements are more than just the kind of pipe you’ll need.

It also includes specific information about clearances and offsets that you need to follow for safe and proper installation.

Before we get started, you’ll need to begin by consulting the owner’s manual for your appliance. Different fireplaces and stoves will have varying requirements.

These requirements are more than just the kind of pipe you’ll need.

It also includes specific information about clearances and offsets that you need to follow for safe and proper installation.

Direct Vent Pipe

Direct vent pipe is made specifically for a direct vent gas appliance, which means they use only outside air for combustion and vents all exhaust directly back outside.

The appliance is sealed from the room by a glass door that should never be opened while the unit is in use.

We see a lot of direct vent units because they are efficient and relatively easy to install compared to wood-burning appliances.

There are two types of direct vent piping systems: coaxial and colinear.

Coaxial Pipes

Coaxial pipes consist of a pipe within a pipe. Basically, this means that there’s a smaller inner pipe fixed inside a larger outer pipe.

The inner pipe, which is separated from the outer pipe by spaces, vents and removes all combustion byproducts and exhaust out of the appliance and out of your home.

The space between the two pipes brings in fresh air from outside the appliance for combustion.

Colinear Pipes

A colinear pipe has two separate pipes. One for combustion air and the other for exhaust.

These are usually flexible and typically use masonry structures to run the piping.

Clearances & Attachments

Clearances for direct vent pipes may vary and the clearance will be specified by the manufacturer of your direct vent appliance.

A general rule of thum is a 1-inch clearance all the way around for vertical vent runs.

If running the pipe horizontally, it must maintain a 3-inch clearance fo the top half of the pipe and a 1-inch clearance for the bottom half.

Direct vent chimneys are very specialized. That means every component is specially made for venting a direct vent appliance. So, you’ll never convert direct vent pipe to class A chimney pipe.

And you’ll never convert a stove pipe to a direct vent pipe.

However, in some cases, you may be able to convert class A chimney pipe into a direct vent system using specialized adaptors.

Direct Vent Termination Cap

A unique and convenient feature of direct vent chimney systems is that you can vent and terminate in multiple ways.

A direct vent system can terminate horizontally or vertically.

Whatever the case, just make sure you follow the manufacturer’s guidelines or maximum horizontal run, vertical rise, etc. when you’re designing your direct vent system.

Direct vent units may be referred to as Top Vent, Rear Vent, or Slant Back. These refer to the position of the flue collar on the appliance.

The top vent and rear vent are self-explanatory. Whereas slant back refers to an appliance with a flue collar coming out of the unit at a 45-degree elbow.

Many direct vent appliance manufacturers will offer specific horizontal or vertical venting kits for particular units.

Vertical Termination Cap

A vertical termination cap is used when terminating vent pipes vertically through a roof.

Depending on the manufacturer of your appliance, there may be some specialization options like a high-wind cap, a low-profile cap (helps protect against rain), or an extended vertical cap.

Some caps are made of aluminum, while others are made of stainless steel. We prefer stainless steel because it lasts much longer and usually has a transferable lifetime warranty.

Horizontal Termination Cap

You’d use a horizontal termination cap when the appliance vents horizontally out the wall instead of up and out of your roof.

Just like with vertical termination caps, you might be able to add in some specialized options, such as round or square caps.

Either way, just be sure to check with your manufacturer’s guidelines for proper clearances for horizontal termination of your unit.

These guidelines will specify the distance you’ll need from your wall, windows, doors, and other parts of your home.

Also, some of the appliances may call for a minimum amount of vent rise before horizontal termination can happen.

Other Components

In addition to the pipe and termination cap, there are still several components that you may need for the installation of your new chimney pipe.

Elbow/Elbow Kit

Elbows are often needed in chimney systems for a variety of reasons.

Unless you are able to vent your chimney system vertically or horizontally without any obstructions blocking your path, you are going to need an elbow of some kind.

All manufacturers specify the offset parameters for each hearth appliance in the owner’s manual. So you’ll want to consult your manual for this specific information regarding your unit.

Elbow Strap/Wall Strap

Many manufacturers provide elbow straps for many kinds of pipe to support chimney systems with offsets.

You’ll use wall straps — one every 4-5 feet of vent rise — when running a direct vent chimney pipe vertically inside a chase or alongside a wall.

Ceiling Support Box/Thimble

These components are necessary for use when the pipe is exposed and exiting the room where the appliance is located.

If you are venting vertically through the ceiling/roof, you will need a ceiling support box or a round ceiling support. If you are venting horizontally through the wall, you will need a thimble.

In direct-vent systems, these will be used only for support, as there is no transition to another kind of pipe.

Firestop/Attic Insulation Shield

When passing through a ceiling, floor, or attic, you will need to use one of these components.

If ceiling support is not used, the firestop is required for passing through ceilings in multi-story homes, while the attic insulation shield is required when passing through an attic.

Both of these pieces ensure your pipe maintains proper clearances as it passes through combustible ceilings and floors.

Chimney Tee/Tee Support

When your chimney system passes through the wall, you will need a tee and tee support to serve as a 90-degree bend to turn your chimney up toward your roof.

Roof Support

Placed underneath the flashing on the roof, the roof support is designed to support pipe both above and below the roof.

There is a limited amount of pipe it will support, particularly below the roof, but this component is ideal if you do not have a ceiling support box as part of your system.

Flashing/Storm Collar

A flashing and storm collar go hand-in-hand. They are designed to protect your chimney system from weather damage.

The flashing is the piece that covers the hole in your roof where the pipe penetrates. The storm collar fits around your pipe just above the flashing to prevent rain or snow from getting into the minuscule crevice between your flashing and pipe.

You need to select a flashing appropriate for your roof pitch. A roof pitch is a measurement of vertical rise over a horizontal distance of 12 inches.

For example, if your roof has a vertical rise of 3 inches over a 12-inch horizontal distance, your pitch is 3/12.

Extended Roof Bracket

When your chimney extends more than 5 feet above your roof, you need an extended roof bracket to provide stabilization for your pipe against the wind.

How to Hire a Chimney Contractor

When you’re ready, you should schedule a time for a certified chimney expert to go to your home to take a look at the area you want your new class A chimney installed.

You can easily reach out to your local chimney company and have a done-for-you solution in no time!

But navigating through all of the chimney companies in your city can be a chore all on its own. And it makes sense, too.

Hiring anyone to come into your home to install a heat source involving fire shouldn’t be a task you take lightly. So I created a list that you can use to make sure you make the right decision when you need someone to help you in your home.


Questions to Ask

When you’re hiring a chimney company, you should always ask the following questions before allowing them to come into your home:

  1. Can the company provide references? 
  2. Does the company carry a valid business liability insurance policy? 
  3. Does the company ensure that a certified chimney technician will be on the job? 

If they guarantee all three of those, then you are in a good spot. The technicians don’t necessarily need to be certified by the CSIA, but I do recommend putting in a bit more due diligence before accepting a certification that’s not by the CSIA. 

This is because certifications are a tricky thing, especially in an unlicensed industry like ours. Any company can craft a list of job-related questions and sell them as an exam and certify those who pass.


I recommend you take a few extra minutes in your research before making your hiring decision to learn more about the certification the company has. Here are a few tips to make sure the certification is reputable: 

  • Is the word “certified” just part of the business name or is it an earned designation? 
  • Is the certifying body a for-profit business or non-profit? 
  • Does the certification need to be maintained and renewed through continuing education as the industry evolves, or is it well enough to be certified through a one-time exam? 
  • Is the certifying body well-established or are they relatively new to the scene? New doesn’t mean “bad” but you should make sure the requirements for certification are more or at least equally stringent as those of more established certifications
  • Is the mission statement of the certifying body focused on educating and protecting homeowners or is it more focused on making it easier to earn a certification? 
  • Does holding the certification require following a code of ethics? 

If you can answer all of these questions, then I think it will be safe to allow the company in your home to work on your chimney. 

Please note that If you are hiring a chimney company to install a cap for you, most of the time, they will need to buy the cap themselves. This is primarily for liability and insurance purposes. 

It doesn’t matter if you are in Roanoke, Lynchburg, Blacksburg, or some other city anywhere in the USA — if you have any questions about the safety of hiring a chimney company, please don’t hesitate to email me at mitchell@patriotchimney.net or call me at 540-225-2626. I’m happy to help!


When you’re shopping for a new fireplace and need a direct vent chimney installed, now you’ll know exactly what you need to look for.

But if you have any questions, feel free to reach out and we’ll be happy to help you figure out the best plan of action.

It doesn’t matter if you are in Roanoke, Lynchburg, Blacksburg, or some other city anywhere in the USA — if you have any questions, please don’t hesitate to email me at mitchell@patriotchimney.net or call me at 540-225-2626.

I’m happy to help!

If you’d like to get started with the process of having Patriot Chimney install your new Class A chimney, fill out the form below and someone from our office will call you in no time!


100% Satisfaction


No Mess Guarantee

CSIA Certified

Proud NCSG Members

Schedule an Inspection!

  • Hidden
  • This field is for validation purposes and should be left unchanged.

Pin It on Pinterest