Hearth and Home Technologies BIR50 Alternate materials worksheet, Position the Hearth Extension

North Star

EPA Certified Fireplace

17. Alternate materials worksheet

How to determine if alternate floor protection materials are acceptable:

All floor protection must be non-combustible (i.e., metals, brick, stone, mineral fiber boards, etc.). Any organic materials (i.e., plastics, wood paper products, etc.) are combustible and must not be used. The floor protection specified includes some form of thermal designation such as R-value (thermal resistance) or k-factor (thermal conductivity).

PROCEDURE:

1. Convert specification to R-value:

				1		x T
R-value given - no conversion needed.			K-factor is given with a required thickness (T) in inches:	R =
					K x 12
k-factor is given with a required thickness (T) in inches: R =	1	x T	r-factor is given with a required thickness (T) in inches: R = r x T
	k

2.Determine the R-value of the proposed alternate floor protector.

i.Use the formula in step (1) to convert values not expressed as “R”.

ii.For multiple layers, add R-values of each layer to determine overall R-value.

3.If the overall R-value of the system is greater than the R-value of the specified floor protector, the alternate is acceptable.

EXAMPLE: The specified floor protector should be 3/4 inch thick material with a k-factor of 0.84. The proposed alternate is 4” brick with an r-factor of 0.2 over 1/8” mineral board with a k-factor of 0.29.

		1	=	1	x 0.75 = 0.893
Step (a): Use formula above to convert specification to R-value.	R = k x T			.84
Step (b): Calculate R of proposed system. 4" brick of r = 0.2, therefore:			1/8" mineral board of k = 0.29, therefore:
Rbrick = 0.2 x 4 = 0.431			Rmineral board		=	1	x 0.125 = 0.431
						0.29

Rtotal = Rbrick + Rmineral board = 0.8 + 0.431 = 1.231

Step (c): Compare proposed system Rtotal of 1.231 to specified R of 0.893. Since proposed system Rtotal is greater than required, the system is acceptable.

DEFINITIONS

(ft2)(hr)(oF)

k = Btu(in) = K x 12

K =

Btu(ft)

2

o

F)=

1

=

Btu

2

(hr)(oF)

r = (ft

)(hr)(

k

2

o

F)

ft

(Btu)(in)

ft

(hr)(

18. Position the Hearth Extension

Position and secure the hearth extension over the

protective metal strips that have been placed partially

under the fireplace front. These strips should be

protruding approximately 2” from under the fireplace

front and 2” on both sides of the fireplace opening.

See Figure 13A on page 13. Seal the crack between

the hearth extension and fireplace with a bead of

noncombustible sealant. See Figure 18A. Apply a

noncombustible finishing material of your choice to the

hearth extension.

NOTE: SEE PAGE 5 “CLEARANCES TO COM-

BUSTILES, HEARTH EXTENSIONS / FLOOR PROTEC-

TION” FOR CLEARANCES REQUIRED FOR DIFFER-

ENT HEARTH EXTENSION INSTALLATIONS. THE

CLEARANCES MUST BE STRICTLY ADHERED TO.

WARNING!

Hearth extensions are to be installed only as illustrated to

prevent high temperatures from occurring on concealed

Seal with non-

combustible materials. Hearth sealing strips prevent

combustible sealant

burning or hot particles from inadvertently falling directly

on combustible surfaces in the event the building should

Figure 18A - Position the Hearth Extension

settle and disturb the original construction.

480-1081

18

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