Lennox Hearth C160, CA160, SWI160 HEARTH PROTECTION, SEE TABLE 3 ON FOLLOWING PAGE FOR CANADA REQUIRE- MENTS

The hearth and/or ﬂoor protection must be a thermally rated non-com-

bustible hearth/ﬂoor protector meeting or exceeding a thermal rating of

k=.84 or equivalent with a listed thickness of 3/8" (9.5mm) minimum in

USA (3/4" - 19mm minimum in Canada). The covering must extend 18”

(450mm) in front of the heater and 8” (200mm) to either side (measured

from door opening in the USA and measured from the side of the unit

in Canada).

Using Alternate Material As Floor / Hearth Protection

The hearth extension or alternate material used as a ﬂoor/hearth protec-

tor must be constructed of a durable noncombustible material having an

equal or better thermal conductivity value (lower k value) of k =.84 BTU/IN

FT2 HR °F or a thermal resistance that equals or exceeds r = 1.19 HR °F

FT2 IN/BTU with a minimum thickness of 3/8” in USA or 3/4” in Canada.

With these values, determine the minimum thickness of the alternate

material required using the formula(s) and shown in Table 2 for USA

and Table 3 for Canada.

Note: Any noncombustible material having a minimum thickness of

3/8”(9.5 mm) for USA or 3/4” (19mm) in Canada whose k value is less

than .84 or whose r value is more than 1.19 is acceptable. If the alternate

material used has a higher k value or lower r value will require a greater

thickness of the material used. In some cases, if the k value is less or

the r value higher, a thinner material may be used.

Methods of determining ﬂoor protection equivalents:

To determine the thickness required for the alternate material when

either the "k" value or "r" value is known, use either the k formula or r

formula.

Example: If Micore 160 Mineral Fiber Board is to be used for the ﬂoor

protection, how thick must this material be?

kM = k value per inch of alternate material

rM = r value per inch of alternate material

TM = minimum thickness required for alternate material

TS = standard thickness of the alternate material

kL = k value per inch of listed material

rL = r value per inch of listed material

TL = minimum thickness of listed material

Note: An asterisk "*" indicates, it is a value taken from Tables 2 and 3.

Using the k formula:

FOLLOWING EXAMPLES ARE CALCULATED FOR USA REQUIRMENTS

Using the k formula:

Minimum k-value (per Inch) of Speciﬁed min.

thickness of = alternate material (kM) x thickness

alternate k-value (per inch) of listed

material (TM) of listed material (kL) material (TL)

TM (inches) = kM x TL

*.84

TM (inches) = *.35 x .375"

*.84

.156 (inches)= .417 x .375"

Answer - The minimum required thickness of the Micore 160 is .156" therefore

round up to nearest standard thickness available which is 3/8” (.375”)

Minimum r-value (per Inch) Speciﬁed min.

thickness of = of listed material x thickness

alternate r-value (per inch) of listed

material of alternate material material

TM (inches) = rL x TL

TM (inches) = *1.19 x .375"

*2.86

.312 (inches)= .416 x .375"

Answer - The minimum required thickness of the Micore 160 is .156"

therefore round up to near est standard thickness available which is

3/8” (.375”)

Using the r formula:

Listed Material

k (per inch) r (per inch) Listed Min. Thickness

Listed Material .84

1.19

3/8" (.375")

** Approved Alternate Materials for Floor/Hearth Protection

Alternative Materials Thermal Values Minimum Thickness

(rounded to nearest 1/8 inch)

k (per inch)

r (per inch)

Min. Thickness

Kaowool M Board .47 2.13 .42" (1/2")

Micore 160™

U.S. Gypsum

.35 2.86 .31" (3/8")

Micore 300™

U.S. Gypsum

.46 2.17 .41" (1/2")

Durock™ Cement Board

U.S. Gypsum

1.92 .52 1.71" (1-3/4")

Hardibacker™ 1.95 .51 1.74" (1-3/4")

Hardibacker 500™ 2.30 .43 2.05" (2-1/8")

Cultured Stone Hearth-

stone™

2.82 .35 2.52" (2-5/8")

Wonderboard 3.23 .31 2.88" (3")

Super Firetemp M

Johns-Manville

.61 1.64 .54" (5/8")

Super Firetemp L

Johns-Manville

.54 1.85 .48" (1/2")

Face brick 9.00 .111 8.04" (8-1/8")

Common brick 5.00 .20 4.46” (4-1/2")

Cement mortar 5.00 .20 4.46” (4-1/2")

Ceramic tile 12.5 .08 11.16" (11-1/4")

Marble ~11 ~.09 9.82" (9-7/8")

Table 2 - USA REQUIREMENTS

** If the hearth extension material(s) that is intended to be used is NOT listed

on Table 1, the material can still be used if the material(s) is noncombustible.

However, the manufacturer of the material must provide either the listed k-value

per inch or r-value per inch with listed thickness so that the minimum thickness

required for the hearth can be calculated (per instructions here or as speciﬁed

in the NFI Certiﬁcation Manuals).

Note: Also see NFI (National Fireplace Institute) Certiﬁcation Manuals show-

ing other acceptable calculation methods and acceptable alternate materials

which can be used.

HEARTH PROTECTIONSEE TABLE 3 ON FOLLOWING PAGE FOR CANADA REQUIRE-MENTS