On cold winter days, burning firewood can be a great choice for heating a home or residence. However, it’s important to remember a few things about buying and using firewood for heat.
Buying Firewood
The most important thing to remember about firewood sales is that they must be measured in cords. The only legal method of selling firewood is by the cord. However, many consumers really cannot tell what a cord is unless it is stacked up and measured.
File photo from Wikimedia Commons
A cord of wood always measures 128 cubic feet – 128 cubic feet of compactly stacked wood in a rectangular form. It can be 4’ X 4’ X 8’ (four feet high by four feet wide by eight feet long). It can be 2’ X 8’ X 8’ (two feet high by eight feet wide by eight feet long. It just has to stack up to 128 cubic feet. The wood should be stacked with the pieces parallel to each other. Wood stacked in a crisscross or log cabin fashion does not meet the legal definition; and most likely the stack will contain less wood than one that is stacked by the legal parallel method. Regulation prohibits the sale of firewood in unspecified quantities such as “load,” “truckload,” “face cord,” “rack,” or “pile.”
If a buyer purchases more than 100 pounds of wood, the seller is required to inform the buyer about the cord equivalent of the purchase of firewood. Fractions of cords are allowed to be sold when identified as such. Buyers should ask sellers to measure the wood to ensure they are getting a full cord. An easy way to measure a cord is a stack of wood eight feet long, four feet wide and four feet high. 
According to the Delaware Forest Service (DFS), people should do their research before getting a trailer-full of firewood and warming up in front of the fire. Firewood from other states and regions should be avoided because of the threat of introducing invasive insects that could severely damage Delaware’s trees. Chief among the threats are the Asian longhorned beetle, which attack maple trees, and the emerald ash borer, which tunnel into ash trees.
“People could come from Maryland or Pennsylvania to camp in Delaware and inadvertently bring these pests,” said a DFS spokesman. “That could be very harmful.”
Buyers should also know that different wood species have different heat values. Hickory, oak and sugar maple burn the hottest, while poplar, cottonwood and eastern white pine put off the least heat. The following chart shows the relative heat outputs of various tree species:
HEAT VALUE OF DELAWARE TREE SPECIES IN BTU’S PER CORD FOR AIR-DRIED WOOD
(WITH 20% MOISTURE CONTENT)
| HIGH | MODERATE | LOW |
| 30-40 million BTU’s | 22-29 million BTU’s | 15-21 million BTU’s |
| American beech | American elm | yellow-poplar |
| American hornbeam (ironwood) | American holly | red alder |
| black birch | baldcypress | eastern cottonwood |
| black locust | black cherry | large-tooth aspen |
| dogwood | black walnut | swamp cottonwood |
| hickories | blackgum | black willow |
| hophornbeam (blue beech) | eastern redcedar | weeping willow |
| osage-orange | green ash | eastern white pine |
| persimmon | red maple | Atlantic white-cedar |
| red mulberry | sassafras | |
| red oaks | slippery elm | |
| river birch | silver maple | |
| sugar maple | southern red oak * | |
| white oak * | Southern yellow pines | |
| white ash | sweet gum |
* Red oaks are distinguished by sharply tipped leaf lobes; white oaks have rounded lobes
Calculation assumes 90 cubic feet per cord of solid wood fiber and 7800 BTU’s per pound of wood, which includes a deduction for the heat of vaporization • Heat values are based on the species’ fiber content (measured in weight).