Metal Chimney 101

Generally your chimney is not something you think about. It’s one of those things you check into when you’re building or if you decide to put in a new stove but it’s not usually an area that people know a lot about. After all…other than having it cleaned there isn’t really a lot to do once it’s in place.


For hundreds of years the chimney has been synonymous with a masonry built structure. Chimneys were built from brick, stone, or perhaps cement cinder blocks in more recent history. The first metal chimney’s appeared in the 1920’s under the brand name “Metalbest”. It later became Metalbestos. It’s the name we all think of for metal chimney’s in the same way we think of Kleenex as tissues. There are many brands of chimney but the Metalbestos brand name has been ingrained in our collective psyche to mean any metal chimney. Both Masonry and metal chimney’s are still used today.

Typical Metal Chimney Installation

In recent years metal chimneys have become the standard for many home builders and home owners alike. There are some clear advantages to using a metal chimney. It may seem counter-intuitive that a metal chimney would have any advantage over a brick built chimney but it does. Chimney construction is governed by NFPA-211(National Fire Protection Association) code or the IRC (International Residential Code). There are strict guidelines that must be followed to ensure a safe and well built chimney. Reputable Masons will be experts in these codes and will build a chimney that will meet the standards and last for years.

Testing Label for ICC Metal Chimney
Testing Label for ICC Metal Chimney

Metal chimney’s also must be installed according to NFPA-211 and/or the IRC. In ADDITION to that they must also be Tested and Listed to the UL (Underwriters Laboratory) standard for high temperature chimneys.


“Class A” metal chimney’s must be tested to the UL-103HT standard here in the United States. This means that before a metal chimney can be offered for sale  the chimney must be sent to a laboratory and actually tested under harsh conditions. There are lots of particulars to the testing that but the big one for our purposes is that the chimney MUST be able to withstand 3 consecutive 10 minute tests at 2100 degrees.  2100 Degrees is the approximate temperature that could be reached during a chimney fire.


In a chimney fire time is everything. Time to get out of the house, time for the fire department to arrive, time to react and time to take action before a chimney fire can become something bigger. The UL testing standard is intended to make sure the chimney you are purchasing can hold up and give you that precious time. Masonry chimneys are not required to be tested. A masonry chimney may hold up fine but because of the variables in site built chimneys there is no test done to determine how it will actually perform.For me there is a clear advantage to using a metal chimney. I sleep better at night knowing the chimney’s we install in our customer’s homes are actually tested under these UL guidelines in addition to being installed according to the codes that cover both metal and masonry chimney’s.


Here at Evergreen Home & Hearth we made the decision to chose a brand of chimney that is also tested to the Canadian standard CAN/ ULC S-629. This standard requires testing to 2400 Degrees rather than the 2100 Degrees required here in the United States. The higher Canadian standard gives us even more peace of mind and speaks to the quality of the product.


The ICC brand chimney we sell is also lighter than many of the other brands which makes it easier to handle during installations. The limited Lifetime Warranty INCLUDES replacement of any components damaged during a chimney fire which is really amazing when you consider the temperatures involved.


Proper installation is vital for safety and required by the manufacturer. If you’re installing your chimney yourself be sure to follow all the manufacture instructions. The easiest way to be sure your new chimney is installed correctly is to have our National Fireplace Institute certified installers do it for you!


By: Mark Higgins