“R value” = 1 = r x thickness of material used k
Example: Given that the required “R value” for a suitable hearth extension used must be equal to or greater than:
“R” = r x TL = 1.19 x 1" = 1.19.
If it is desired to elevate a marble hearth extension to a level of 5" or more above the floor surface. What combination of noncombustible materials can be used to accomplish this?
If common brick is used so that the 3 ¹⁄₂" dimension is the height, “R” for the common brick becomes:
“R”M = r x TM = 0.20 x 3 ¹⁄₂" = .70
Using ¹⁄₂" of mortar to set the brick, “R” for the mortar is calculated as follows:
“R”M = r x TM = 0.20 x ¹⁄₂" = .10
A ³⁄₄" marble slab set in ¹⁄₂" mortar covers the brick, “R” for the marble and mortar becomes:
“R”M = r x TM = 0.09 x ³⁄₄" = .068 “R”M = r x TM = 0.20 x ¹⁄₂" = .10
The sum of all “R values” is:
.70 + .10 +. 068 + .10 = .968
This would not be an acceptable combination of material for the hearth extension since the total calculated “R value” of the materials used is under the required “R value” of 1.19. An additional layer of insulating materials must be used.
WARNING: THE CRACK BETWEEN THE FIREPLACE AND THE HEARTH EXTENSION MUST BE SEALED WITH A NON- COMBUSTIBLE MATERIAL.
WARNING: WHEN INSTALLING THE HEARTH EXTENSION BE CAREFUL NOT TO BLOCK THE
20
WARNING: WHEN INSTALLING HEARTH EXTENSION IN FRONT OF THE FIRE- PLACE, THE FIREPLACE MUST BE RAISED IF HEIGHT OF HEARTH EXTENSION EXCEEDS 5 3/4" ABOVE BOTTOM OF FIREPLACE (FIGURE 59 ).
*5 ¹⁄₈" (130 mm) If “C” Style Door Is Used.
5⁵⁄₈"*
(143 mm)
Max.
Maximum Thickness of Hearth Extension when Fireplace is on the Floor.
Figure 59
FINISH TO YOUR TASTEThere are a wide variety of “finished looks” for your CST and CPF fireplace from formal wall decor with elaborate mantels to rustic wood paneling or warm brick facings.
Only noncombustible materials like marble, stone, tile, brick, etc. may overlap the black front facing, but be careful not to interfere with the operation of the glass doors. Seal all joints between the black facing and wall surrounds to prevent cold air intrusion. Use noncombus- tible caulking material only to seal the black metal facing to the surround material on the finished wall.
Combustibles may also project beyond the sides of the fireplace opening as long as they are kept within the shaded areas, as illustrated in Figures 60 and 61.
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
Combustible
Materials Allowed
in Shaded Area
4⁵⁄₈"
(118 mm) | 1" (25 mm) |
30˚ 11 ³⁄₈"
(289 mm)
8" (203 mm)
Minimum Distance to Protected Side Wall
18" | Minimum Distance |
(457 mm) | to Unprotected Side Wall |
Model
Figure 60
Combustible
Materials Allowed
in Shaded Area
1" (25 mm)
30˚
8" (203 mm)
Minimum Distance to Side Wall
Model
Figure 61
ACCESSORY PARTS AND COMPONENTS LIST FOR MODELS
The accessory parts and components shown on pages 21 and 22 are to be used only with your
If you encounter any problems or have questions concerning the installation or application of this system, please contact your distributor. For the name of your nearest distributor call:
LENNOX HEARTH PRODUCTS
1110 West Taft Avenue
Orange, CA 92865
Model | Part Number | Weight |
051991 | 215 lbs. | |
052011 | 210 lbs. |