Metal Chimneys for Gas Fireplaces

A note about metal chimneys for gas fireplaces and woodstoves.

There are three main types of metal chimneys: air insulated, plain, and solid pack. Solid pack chimneys are often called “Class A” chimneys.

Woodstoves are usually installed using plain pipe chimneys. To find the right size chimney cap all you need to do is measure the inside diameter of the pipe. For example, an 8” chimney cap will fit snugly inside an 8” flue.

There are two pipes for air insulted flues, one larger than the other with an air pocket in the middle. Some flues have a third pipe that helps to create a more pleasing look. You will want to pick a chimney cap that has been specially designed for an air-insulated flue, making sure to choose one that covers both the air jacket and any decorative jacket.

Solid flues are comprised of two pipes with air in between them. Like air insulated flues, some solid flues also have a decorative outer pipe. Be sure to find a chimney cap designed to work with a solid flue and large enough to cover the outer pipe, either the insulation jacket or the decorative jacket if there is one.