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FV33i Gen 3
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3.2.13
Hearth Pad Requirement
A non-combustible hearth protector with a thermal insulation rating of R-1 is required when installing this insert directly on the
floor and must extend a minimum of 16" in front of this insert.
For every 1” the insert is raised off the floor, the depth of the required R-1 hearth protector may be reduced
by 2”.
If the insert is raised off the floor 6" or more, no R-1 hearth protector is required for fire protection.
Raising the insert only removes the requirement for a R-1 rated hearth protector. The floor in front of the
insert will still get hot up to 200 °F. The higher the insert is raised the lower the temperatures on the floor
will be. Materials used on the floor in front of the insert must be appropriate for elevated temperatures.
Flooring materials such as carpet, vinyl and laminated floors may warp or be damaged if installed in front of
this insert. If these materials are used it is recommended that the insert is raised at least 12” above the
floor.
Mendota does not guarantee any materials used around the insert. Mendota disclaims any and all liability for
any damage to finishing materials including warping, discoloring, cracking, peeling or flaking. This also
includes any off-gassing or unpleasant smells from materials when they are heated.
Hearth Pad Materials
A hearth pad with an R-Value of at least 1 is required unless the insert is raised off the floor 6” or more. A list of common
finishing materials and their R-Values is included in the “R-Values of Common Finishing Materials” section of this manual. Many
finishing materials have a low R-Value. For example, 1” thick granite has a R-Value of only .05. When building a conforming
hearth pad it may be necessary to use an insulating underlayment board with a high R-Value. A list of some possible
underlayment boards is given below. These boards are not structural they can be easily dented and damaged. They must only be
used as an insulator under other non-combustible finishing material.
R-Values of Hearth Pad Boards
Material
Thickness
R-Value
Application
Mineral Fiber Board ( Micore 160, 300, SB)
1/2"
1.27 – 1.47
Hearth Pad Insulator
Cearmic Board (Rescor 360)
1/2"
1.11
Hearth Pad Insulator
Cearmic Board (Fiberfrax Duraboard LD)
1/2"
1.10
Hearth Pad Insulator
