17
WR / WC Series Woodburning Fireplace
20014528
COMMON MATERIALS AND FACTORS
MATERIAL
K*
R
MINIMUM
THICKNESS
EH2416
Common Brick
0.458
5.0
1.09
0.50 in.**
0.10 5.46 in.**
(MHSC)
R Value is for 1/2 inch.
* Units of K = BTU/SQ FT/HR
/˚F/IN
** Thickness of Listed Material
FP533ADD
Addendum
6/1/99 djt
8/4/99 changed .2 to .1
one inch to 1/2 inch djt
FP533ADD
WARNINg: HeARTH eXTeNSION MUST be IN-
STALLeD IN ACCORDANCe WITH FIgURe 23 AND
MUST NOT COVeR THe bOTTOM FRONT OPeNINg
OF THe CIRCULATINg MODeL.
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.
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
equivalents
To determine the thickness required for any
new
mate-
rial:
example for Common brick
T (new) = 5.0/0.458 x 0.50 in. =
5.46 in.
(new required
thickness).
Fig. 24
Hearth extension material factors.
FP550
Fig. 25
Sealing gaps.
FP550
BR/BC - SEALING
DETAILS
9/29/97
Wall Covering
Noncombus-
tible Decorative
Facing
2 x 4 Header
(Do not notch
at standoffs)
Seal all cracks
between fireplace
surround and wall
materials with noncom-
bustible material
Noncombustible
Decorative Cover-
ing
Hearth Extension
Insulation
Safety Strips
Must be overlapped 1/2"
minimum
Seal crack between
fireplace and hearth
extension with noncom-
bustible material
Side View
NEW
K of new material (per inch)
thickness
required =
X of listed
thickness K of listed material (per inch) material
