Finishing, A. non-combustible materials, B. combustible materials – Hearth and Home Technologies HST-48D User Manual

Page 38: Table 11.2 c. hearth extension, Table 11.1, R = 1/k x inches of thickness

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38

11

11

Finishing

A. Non-Combustible Materials

• Materials which will not ignite and burn, composed of

any combination of the following:
- Steel

-

Iron

- Brick

- Tile

- Concrete

- Slate

- Glass

- Plasters

• Materials reported as passing ASTM E 136, Standard

Test Method for Behavior of Metals, in a Vertical Tube
Furnace at 750° C

B. Combustible Materials

• Materials made of or surfaced with any of the following

materials:
- Wood

- Compressed

paper

- Plant

fi bers

- Plastic

• Any material that can ignite and burn; fl ame proofed or

not, plastered or un-plastered

A

B

C

Figure 11.1 Hearth Extension Dimensions

Table 11.2

C. Hearth Extension

WARNING! Risk of fi re! High temperatures, sparks,
embers or other burning material falling from the fi replace
may ignite fl ooring or concealed combustible surfaces.
• Protective metal hearth strips MUST be installed.
• Hearth extensions MUST be installed exactly as

specifi ed.

Table 11.1

Hearth Extension Insulation Alternatives-Total minimum R Value must equal 1.03

Material

k per inch

thick

r per inch

thick

Minimum

thickness

required

Hearth & Home HX3, HX4 (Micore 300™)

0.49

2.06

1/2 in.

USG Micore 160™

0.39

2.54

1/2 in.

USG Durock™ Cement Board

1.92

0.52

2 in.

Cement Mortor

5.0

0.20

5-1/8 in.

Common Brick

5.0

0.20

5-1/8 in.

Ceramic Tile

12.50

0.08

12-1/4 in.

Armstrong™ Privacy Guard Plus

0.46

2.18

1/2 in.

Marble

14.3-20.0

0.07-0.05

14-5/8 in. - 20-3/8 in.

R = 1/k x inches of thickness

• You MUST use a hearth extension with this fi replace.
• This

fi replace has been tested and approved for use with

a hearth extension insulated to a minimum R value of
1.03.

• The hearth extension material MUST be covered with

tile, stone or other non-combustible material.

• Manufactured hearth materials will usually have a

published R value (resistance to heat) or k value
(conductivity of heat). Refer to the formula in Table 11.1
to convert a k value to an R value,

• Refer to Table 11.2 for hearth extension insulation

alternatives.

CAT. #

A

B

C

HX4

in

66

20

12

mm

1676

508

305

Heat & Glo • HST-48D US-CAN • 4012-040 • Rev F • 11/08

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