The Chimney Sweep Online Fireplace, Woodstove, Gas Stove and Barbecue Shop
The Chimney Sweep Online Fireplace, Woodstove, Gas Stove and Barbecue Shop
Sweep's Library:
Q: My new woodstove's installation manual calls for a non-combustible hearth (floor protection) extending so many inches beyond the rear and
sides of the stove and in front of the loading door. This much I understand. The manual also states this floor protection must have an "R" value of
at least 0.800. This part I don't understand: what is an R value, and how do I ensure that my hearth material meets the minimum requirement?
|
| Material | Thickness | R-Value |
| Mineral Fiber Board ( Micore 160 ) | 1/2" | 1.270 |
| Ceramic Board ( Rescor 360 ) | 1/2" | 1.110 |
| Ceramic Board ( Fiberfrax Duraboard LD ) | 1/2" | 1.100 |
| Mineral Fiber Board ( Micore 300 ) | 1/2" | 1.030 |
| Common Brick | 4" | 0.800 |
| Common Brick | 2-1/4" | 0.450 |
| Gypsum or Plaster Board | 1/2" | 0.450 |
| Cement Board ( Durock Next Gen) | 1/2" | 0.390 |
| Cement Board ( Wonderboard ) | 1/2" | 0.260 |
| Cement Board ( Hardibacker 500 ) | .42" | 0.200 |
| Limestone | 1" | 0.153 |
| Cement Board ( Hardibacker ) | 1/4" | 0.130 |
| Cement Mortar | 1/2" | 0.100 |
| Slate | 1" | 0.100 |
| Concrete | 1" | 0.095 |
| Marble | 1" | 0.090 |
| Granite | 1" | 0.083 |
| Ceramic Pavers | 1" | 0.080 |
| Flagstone | 1" | 0.079 |
| Sandstone | 1" | 0.079 |
| Ceramic Tile | 1/4" | 0.020 |
As the chart shows, you can achieve the required R-value of 0.800 with 1/2" of Fibrefrax or Micore, 8-1/2" of poured concrete, or one layer
of 4" brick. You can also meet your requirement by stacking layers of the materials listed: ie, 4 layers (1.68") of .42" Hardibacker would give you
the 0.800 R-value you require.
