Heatiator I80 Finishing, Fire Risk, 1 Hearth Extension Construction, Minimum, Material

8 Finishing

A. Hearth Extension

A hearth extension must be installed with all fireplaces to protect the combustible floor in front of the fireplace from both radiant heat and sparks. See Figures 8.1-8.5.

	High temperature
	(300°F min.) continuous,
HX3 or HX4	non-combustible sealant		Fireplace
	non-combustible material			Protective
insulation
Hearth Ext	Tile, stone or other
or equivalent
(see Table below)				Metal Hearth
				Strip
		2 in. (51 mm)
Floor constructed of wood or		required
other combustible material

Figure 8.1 Hearth Extension Construction

WARNING

Fire Risk

•Metal hearth strips MUST be installed. Sparks or embers may ignite flooring.

This fireplace has been tested and approved for use with a hearth extension insulated to a minimum R value of 1.03.

To substitute materials for the factory-available hearth ex- tensions, calculate insulation alternatives as per Table 8.1 and the following formulas:

1 in. overlap

Metal strips are placed 2 in. (51 mm) under the front of the fireplace and must extend beyond the front and sides of fireplace opening by 2 in. (51 mm).

Figure 8.2 Positioning the Protective Metal Hearth Strips

WARNING

Fire Risk

•Hearth extensions must be installed exactly as specified.

High temperatures or hot embers may ignite concealed combustibles.

•Thermal conductivity per inch thickness = k

•k = (BTU)(inch) / (foot2)(hour)(°F)

•Required thickness = Rk

•Thermal resistance per inch thickness = r

•r = (foot2)(hour)(°F) / (BTU)(inch)

•Required thickness = R / rB.

Table 8.1

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

			Minimum
	k per inch	r per inch	thickness
Material	thick	thick	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.

30 Heatilator • I80 CAN-US • 4013-203 Rev F • 04/08