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HEI240 Wood Insert Fireplace Installation and Operation Manual
8.4.2 Installation raised more than 5"
If the extension of the masonry hearth is raised at least 5" (127 mm) from the floor
protection
(F)
, a non-combustible material without an R value must extend at least 16"
(406 mm USA) or 18” (457 mm Canada) in front of the unit
(B)
.
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 1.00 is
required and should extend at least 23" (584 mm) in front of the unit.
8.4.3 R Value
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.
To calculate the total R factor from R factors of the materials used, simply add the R-
values of materials. If the result is equal to or greater than the R-value requirements, the
combination is acceptable. To know the R-values of some selected materials, see table
Thermal Characteristics of Common Floor Protection Materials
.
Example:
Required floor protection R of 1.00. Proposed materials: four inches of brick and one
inch of Durock
®
board
Four inches of brick (R = 4 x 0,2 = 0,8) plus 1 inch of Durock
®
(R = 1 x 0.52 = 0.52).
0.8 + 0.52 =
1.32
.
This R value is larger than the required 1.00 and is therefore
acceptable
