CW2500 Insert Installation and Operation Manual
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If the extension of the masonry hearth is raised at least 8" (F) from the floor protection, a
non-combustible material without an R factor extending 16 " (406 mm) (USA)/18’’ (457
mm) (CAN) from the front of the insert is required.
If non-combustible material floor protection needs to be added in front of and level with the
hearth extension of the masonry fireplace, an R factor equal to or greater than 2 is
required.
The use of an R value is convenient when more than one material is going to be used in
the hearth extension to cover the combustible surface. This is because R values are
additive, whereas K values are not.
There are two ways to calculate the R factor of the floor protection. First, by adding the R-
values of materials used, or by the conversion if the K factor and thickness of the floor
protection are given.