Round Metal Chimneys

When it comes to metal chimneys you will usually find three types: double-wall solid-pack insulated chimney pipe, double-wall air-insulated chimney pipe, and triple-wall air-insulated chimney pipe.

You can figure out which type you have by looking down your chimney pipe. When looking at a double wall pipe you will see two pipes, one inside and one outside. When you look at the gap between the pipes you will see one of these three things: insulation, air, or a metal plate blocking your view. If you see insulation or a metal plate you have a solid-pack pack insulated chimney pipe. You have an air-insulated chimney pipe if you see nothing but air. Most triple wall chimney pips will be air-insulated.

Double-Wall Solid-Pack Insulated Chimney Pipe
You should measure the diameter of the interior pipe first, and then measure the diameter of the exterior pipe. You will order your cap using the measurement from the interior pipe. While you will want to cover the outer pipe to keep out the elements, it is fine if the cap overlaps it. Rain will be blocked from entering as long as the exterior pipe is covered. For example, if you have an interior pipe that measures 6” and an exterior pipe that measures 8” you will want to order a 6” cap that has a bottom ring that is larger than 8”.

Double-Wall or Triple-Wall Air-Insulated Chimney Pipe
You will need to measure the diameter of the interior pipe, and then measure the diameter of the exterior pipe. If you have a triple-wall pipe you can ignore the middle pipe. You will use the measurement from the interior pipe to order your cap. The exterior pipe will need to be covered to ensure that rain can not enter the pipe. For example, if your interior pipe measures 6” and your exterior pipe measures 12 3/8" you will need to order a 6” cap with a bottom ring that is larger than 12 3/8”.

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