Selecting the Right Round Chimney Cap for Round Flues:

What Kind of Round Flue Do I Have?

Your round chimney flue will need the correct type of round chimney cap, one that corresponds to the way it is constructed. There are 6 types of round flues; the type of round flue you have determines which chimney caps for round flues will work for you.

With any existing chimney cap removed, look down your flue and match it with one of the drawings below. The discussion next to the drawing will tell you what kind of flue you have and what types of round chimney caps are appropriate.

Double Wall Air Insulated Flue

Chimney Caps for Round Flues - Double-Walled FluesThe drawing at the left shows a double wall air cooled flue. The flue has an air jacket outside of it. Air circulating between the two walls cools the flue. For this reason, you’ll need a round chimney cap made expressly for a double wall air cooled flue. The chimney caps below are all designed to let cooling air circulate properly in the air jacket. Choices include:


Triple Wall Air Cool, Triple Wall Air Insulated Flue

Chimney Caps for Round Flues - Triple Walled Air Cooled FluesTriple wall air cooled flues, sometimes called triple wall air insulated flues, have two air jackets surrounding a central flue pipe. Air circulating inside the air jackets cools the flue. You can use exactly the same chimney caps described above for double wall air cooled flues, because all three are designed for use with double wall or triple wall air cooled round flues.


Solid Pack Flue or Double Wall Insulated Flue

Chimney Caps for Round Flues - Solid Pack FluesSolid pack flues have insulation sandwiched between two layers of metal. These are sometimes called double wall insulated flues or solid packed insulated flues. In most, the insulation is sealed in by metal ring at each end of a section of flue pipe. When you look down the flue, you will see these seals, not the insulation material itself.

Chimney caps for round flues that have covered insulation include:

Solid Pack Flue with Exposed Insulation

Chimney Caps for Round Flues - Exposed Insulation Round FluesWhen you look down your flue pipe you may see exposed insulation material between an inner metal pipe and an outer one. If so, you have a solid pack flue with exposed insulation. These flues need the same chimney caps used with air cooled flues, so that the insulation material is protected from the elements:


Masonry Clay Flue, Terra Cotta Flue Pipe

Chimney Caps for Round Flues - Clay Masonry Flues


Pictured at the left is a clay flue, which is also called a masonry flue.

These are pipes made of terra cotta—like a flower pot.

Appropriate chimney caps for round flues made of clay masonry  include:


Single Metal Pipe such as a Stovepipe

Chimney Caps for Round Flues - Stove Pipe Flues

This photo shows a single wall metal stove pipe. It’s just a metal tube.

You can use with metal, single wall flues the following chimney caps for round flues:



Round Flexible Metal Flue Liner

Chimney Caps for Round Flues - Flexible Flue Liners


When chimney professionals re-line chimneys, they may use a flexible metal flue liner, like the one shown at the left.

Round chimney caps used with flexible metal liner include:

If you need chimney caps for round flues, the most critical step in the process is determining what type of round flue you have by matching these images with your flue pipe. Then you can get the a chimney cap that will safely and correctly cover your type of round flue.