Vermont Castings EWF36A
Examples of wall shield insulation:
1. Manville - CERAFORM 126, K=.27, 1/2 inches thick
2. EH2416, K = .458,
1 inch thick required.
Hearth Installation
A hearth extension is required to protect a combustible floor in front of the fireplace. Refer to Figure 26 for mini- mum dimensions and mounting detail.
NOTE: Hearth Extension must not cover the air inlet opening of a fireplace.
The hearth extension described in Figure 26 must be a durable noncombustible material with a minimum (total) Rt value of 1.09; refer to Figure 24 for examples. The overall height (above a combustible floor), depth and width must be as indicated, with the extension centered
Noncombustible material with a lower R value may be used, provided thickness of material is sufficiently greater to maintain an equivalent (total) thermal resis- tance (Rt).
Example of Determining Hearth Extension Equivalents
To determine the thickness required for any new mate- rial:
NEW | K of new material (per inch) | thickness | |
required = |
| X | of listed |
| |||
thickness | K of listed material (per inch) | material | |
Example for Common Brick
T (new) = 5.0/0.458 x 0.50 in. = 5.46 in. (new required thickness).
to the fireplace opening.
The top of insulation must be covered with a
Secure the hearth extension to the floor to prevent shifting, using trim molding or other similar means at three (3) outer edges. Seal crack between the fireplace hearth and hearth extension with a noncombustible
Wall Covering 
Noncombus- tible Decorative Facing
Seal all cracks between fireplace sur- round (steel) and wall materials with noncom- bustible material.
2 x 4 Header - Do not notch at standoffs
NOTE: No material may cover black cast face.
material. (Figs. 25 and 26)
WARNING: Hearth extension must be installed in accordance with Figure 25. Top of hearth extension must be level with bottom of fireplace.
Alternate noncombustible materials may be used providing the (total) thermal resistance (Rt value) of the alternate material employed is greater than or equal to R = 1.09 Thermal resistance (R) or thermal conductivity (K), may be obtained from manufacturer of the material. Factors are related by the formula K = 1/R. (Fig. 24)
T = given thickness
R = thermal resistance for a given thickness (T) K = thermal conductivity
COMMON MATERIALS AND FACTORS
Cast Front
Noncombustible |
Decorative Cover- |
ing |
FP1202 | Safety Strips - Must be |
overlapped 1/2” minimum |
Fig. 25 Sealing gaps.
MATERIAL | K* | R | MINIMUM | |
THICKNESS | ||||
EH2416 | 0.916 | 2.18 | 1.0 in.** | |
(CFM Corporation) | ||||
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Common Brick | 5.0 | 0.10 | 5.46 in.** | |
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R Value is for 1/2 inch.
*Units of K = BTU/SQ FT/HR/˚F/IN ** Thickness of Listed Material
FP533ADD
Fig. 24 Hearth extension material factors.
16 | 20005167 |