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Engineering ToolBox > Wood and Combustion Heat Values
The type of wood burned, whether hardwood or softwood, is important for the heat value and the energy efficiency.
Hardwoods have less resin and burn slower and longer. Softwoods burn quickly. In addition to the type of wood, the seasoned length of the wood influence on the fuel efficiency. Seasoning the wood refers to the allowed drying time before burning.
Moisture reduces the woods fuel value and wood need to be dried at least 4 to 6 months before used.
The table below can be used to indicate density and heat value of some common wood species.
| Wood Species | Density of Dry Wood (lb/ft3) | Weight of Dry Cord (lb) | Heat Value of Cord (Green Wood) (millions Btu) | Recoverable Heat Value of Cord (Dry Wood) (millions Btu) | Units needed to produce 1 Million Btu's |
| Apple | 48.7 | 4,100 | 26.5 | 18.55 | 0.054 |
| Aspen | 27 | 2,290 | 14.7 | 10.29 | 0.097 |
| Balsam Fir | 26.3 | 2,236 | 14.3 | 10.01 | 0.10 |
| Basswood | 24.8 | 2,108 | 13.5 | 9.45 | 0.106 |
| Beech | 44.2 | 3,757 | 24 | 16.8 | 0.060 |
| Black Ash | 35.2 | 2,992 | 19.1 | 13.37 | 0.075 |
| Black Spruce | 29.2 | 2,482 | 15.9 | 11.13 | 0.090 |
| Box elder | 32.9 | 2,797 | 17.9 | 12.53 | 0.080 |
| Cherry | 36.7 | 3,121 | 20 | 14 | 0.071 |
| Cottonwood | 24.8 | 2,108 | 13.5 | 9.45 | 0.106 |
| East Hop hornbeam | 50.2 | 4,267 | 27.3 | 19.11 | 0.052 |
| Elm | 35.9 | 3,052 | 19.5 | 13.65 | 0.073 |
| Hackberry | 38.2 | 3,247 | 20.8 | 14.56 | 0.069 |
| Hemlock | 29.2 | 2,482 | 15.9 | 11.13 | 0.090 |
| Hickory | 50.9 | 4,327 | 27.7 | 19.39 | 0.052 |
| Jack Pine | 31.4 | 2,669 | 17.1 | 11.97 | 0.084 |
| Norway Pine | 31.4 | 2,669 | 17.1 | 11.97 | 0.084 |
| Paper Birch | 37.4 | 3,179 | 20.3 | 14.21 | 0.070 |
| Ponderosa Pine | 28 | 2,380 | 15.2 | 10.64 | 0.094 |
| Red Oak | 44.2 | 3,757 | 24 | 16.8 | 0.060 |
| Red Maple | 34.4 | 2,924 | 18.7 | 13.09 | 0.076 |
| Sugar Maple | 44.2 | 3,757 | 24 | 16.8 | 0.060 |
| Tamarack | 38.2 | 3,247 | 20.8 | 14.56 | 0.069 |
| Yellow Birch | 43.4 | 3,689 | 23.6 | 16.52 | 0.061 |
| White Ash | 43.4 | 3,689 | 23.6 | 16.52 | 0.061 |
| White Oak | 47.2 | 4,012 | 25.7 | 17.99 | 0.056 |
| White Pine | 26.3 | 2,236 | 14.3 | 10.01 | 0.100 |
Note that in the table above 1 cord = 85 ft3 is used between to convert between the "Density" and "Weight of Cord" column. Be aware that the densities used for the wood species may vary significantly. The densities used above is for natural dried wood where the average moisture is approximately 20%.
Heat values of Cords with dry wood can be estimated by adding the green wood cords values with approximately 10%.
Recoverable heat values are calculated with a stove efficiency of approximately 65%.