Vermont Casting Common Materials And Factors, Vermont Castings EWF30, Equivalents, 20008662

Vermont Castings EWF30

The top of insulation must be covered with a non-com- bustible decorative covering or a piece of .018” mini- mum sheet metal, to protect hearth extension material. (Fig. 25)

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

material. (Figs. 24 and 25)

WARNING: Hearth extension must be installed in accordance with Figure 24. 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. 23)

T = given thickness

R = thermal resistance for a given thickness (T) K = thermal conductivity

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

COMMON MATERIALS AND FACTORS

MATERIAL	K*	R	MINIMUM
			THICKNESS
EH2416	0.916	2.18	1.0 in.**
(CFM Corporation)
Common Brick	5.0	0.10	5.46 in.**
R Value is for 1/2 inch.
* Units of K = BTU/SQ FT/HR/˚F/IN
** Thickness of Listed Material				FP533ADD

Fig. 23 Hearth extension material factors.

Equivalents

To determine the thickness required for any new mate- rial:

Example for Common Brick

NEW	K of new material (per inch)		thickness
required =		X	of listed
thickness	K of listed material (per inch)		material

T (new) = 5.0/0.458 x 0.50 in. = 5.46 in. (new required thickness).

	2 x 4 Header - Do not
Wall Covering	notch at standoffs
	Noncombustible
Noncombustible
	Material
Decorative
Facing
Seal all cracks	NOTE: No
between fireplace sur-	material
round (steel) and wall	may cover
materials with noncom-	black cast
bustible material.	face.
Cast Front
Noncombustible
Decorative
Covering
FP1202a	Safety Strips - Must be
	overlapped 1/2” minimum

Fig. 24 Sealing gaps.

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