Why do we see 2100 chimneys with two inches of insulation and others with only one inch?

2100 chimneys must pass very stringent temperature tests. In order to pass those tests, manufacturers must use insulation. There are many different types of insulating materials, with varying density and quality. This affects the thickness that the chimney walls must have. Ventis uses a high performance insulating material that enables the chimney walls to be approximately one inch thick. Furthermore, the material's performance allows the passage of Ventis chimney lengths into an enclosed space without the addition of a protective shield. Most other chimney brands require a shield when passing through an enclosed space.