Green weight is the weight of a cord of freshly cut wood before drying. Dry weight is the weight of a cord after air drying. Green firewood may contain 50 percent or more water by weight. Green wood produces less heat because heat must be used to boil off this water before combustion can occur. Green wood also produces more smoke and creosote than dry wood. Firewood always should be purchased dry or allowed to dry before burning.
Dry wood may cost more than green wood because it produces more heat and is easier to handle. A wood's dry weight per volume, or density, is important because denser or heavier wood contains more heat per volume. It is much better to buy or gather dense woods such as oak, ash or mulberry.
Hardwoods, or woods from broadleaved trees, tend to be denser than softwoods, or woods from conifers. Some firewood dealers sell "mixed hardwood" firewood. This may or may not be desirable, depending on the proportion of low-density hardwoods, such as cottonwood, that are included.
Woods that form coals are good to use in wood stoves because they allow a fire to be carried overnight effectively.
Fragrance and tendency to smoke and spark are most important when wood is burned in a fireplace. Woods that spark or pop can throw embers out of an open fireplace and cause a fire danger. Conifers (pines, etc.) tend to do this more because of their high resin content. Woods such as pine, and especially locust contain high volumes of pitch and/or creosote, which can cause a buildup of flammable materials inside the flue of a fireplace chimney or woodstove. Even though some Locust entries in the table below are rated as good or excellent, try to avoid any burning of high-pitch woods.
Firewood from different species or types of trees varies widely in heat content, burning characteristics and overall quality. The table below presents important burning characteristics for many species. This table also contains information on other characteristics that determine firewood quality. Ease of splitting is important because larger pieces of wood usually must be split for good drying and burning.
Wood should be dried as much as possible before burning. Properly seasoned wood has about 7,700 BTUs maximum usable energy per pound versus only about 5,000 BTU available from green wood. For best results, season or air-dry wood for at least six to eight months after cutting. This should bring the moisture content down to 15 to 20% by weight.
The best time to cut wood is during the winter or early spring before the sap runs. If the tree is felled when fully leafed out, let it lie until leaves have become crisp to allow leaves to draw out as much moisture as possible from the tree before further cutting.
Drying time is greatly reduced if wood is cut into firewood length and split, especially when the original pieces are larger than 8 inches in diameter. Splitting is easiest when wood is frozen or green and should be done before wood is stacked. Wood must be properly stacked for satisfactory drying. The greater the surface area exposed to air, the more rapid the drying. Therefore, stack wood loosely and keep it off moist ground. The stack should be located in an open area for good air circulation--avoid stacking in wood lots for seasoning.
Store firewood outdoors, under partial or full protection from the elements, and no closer than 25 feet from the house. Keep area around wood clear of weeds, leaves, debris, etc., to discourage rodents, snakes, insects, and other unwanted pests from making their home in the stacked wood. Avoid storing large quantities in the house, warm garage or basement because the heat will activate insect and fungi or spore activity and bring about hatching of any insect eggs in or on the wood.
All firewood contains water. Freshly cut wood can be up to 45% water, while well seasoned firewood generally has a 20-25% moisture content. Well seasoned firewood is easier to start, produces more heat, and burns cleaner. The important thing to remember is that the water must be gone before the wood will burn. If your wood is cut 6 months to a year in advance and properly stored, the sun and wind will do the job for free. If you try to burn green wood, the heat produced by combustion must dry the wood before it will burn, using up a large percentage of the available energy in the process. This results in less heat delivered to your home, and literally gallons of acidic water in the form of creosote deposited in your chimney.
Wood is composed of bundles of microscopic tubes that were used to transport water from the roots of the tree to the leaves. These tubes will stay full of water for years even after a tree is dead. This is why it is so important to have your firewood cut to length for 6 months or more before you burn it, it gives this water a chance to evaporate since the tube ends are finally open and the water only has to migrate a foot or two to escape. Splitting the wood helps too by exposing more surface area to the sun and wind, but cutting the wood to shorter lengths is of primary importance.
There are a few things you can look for to see if the wood you intend to purchase is seasoned or not. Well seasoned firewood generally has darkened ends with cracks or splits visible, it is relatively lightweight, and makes a clear "clunk" when two pieces are struck together. Green wood on the other hand is very heavy, the ends look fresher, and it tends to make a dull "thud" when struck. These clues can fool you however, and by far the best way to be sure you have good wood when you need it is to buy your wood the spring before you intend to burn it and store it properly.
Apple
Ash, Green
Ash, White
Basswood (Linden)
Birch, Paper
Boxelder
Buckeye, Ohio
Catalpa
Cherry, Black
Coffeetree, Kentucky
Cottonwood
Douglas-Fir
Elm, American
Elm, Red
Elm, Siberian
Fir, Concolor
Hackberry
Hickory, Bitternut
Hickory, Shagbark
Honeylocust
Ironwood
Juniper, Rocky Mountain
Locust, Black
Maple, Other
Maple, Silver
Mulberry
Oak, Bur
Oak, Red
Oak, White
Osage-Orange
Pine, Eastern White
Pine, Jack
Pine, Ponderosa
Redcedar, Eastern
Spruce
Sycamore
Walnut, Black
Willow
27.0
20.0
24.2
13.8
20.8
18.3
13.8
16.4
20.4
21.6
15.8
20.7
20.0
21.6
20.9
14.6
21.2
26.7
27.5
26.7
27.9
21.8
27.9
25.5
19.0
25.8
26.2
24.6
29.1
32.9
15.6
17.2
16.2
18.2
15.5
19.5
22.2
17.6
4850
4184
3952
4404
4312
3589
4210
4560
3696
3872
4640
3319
4456
4800
3800
3585
3984
5032
5104
4640
4590
3535
4616
4685
3904
4712
4960
4888
5573
5120
2780
3200
3600
2950
2800
5096
4584
4320
3888
2880
3472
1984
2992
2632
1984
2360
2928
3112
2272
2970
2872
3112
3020
2104
3048
3832
3952
3832
4016
3150
4016
3680
2752
3712
3768
3528
4200
4728
2250
2488
2336
2632
2240
2808
3192
2540
Low
Low
Low
Medium
Medium
Medium
Low
Medium
Low
Low
Medium
High
Medium
Medium
Medium
Medium
Low
Low
Low
Low
Medium
Medium
Low
Low
Low
Medium
Low
Low
Low
Low
Medium
Low
Medium
Medium
Medium
Medium
Low
Low
Medium
Easy
Medium
Easy
Medium
Difficult
Medium
Difficult
Easy
Medium
Easy
Easy
Difficult
Easy
Difficult
Easy
Easy
Medium
Difficult
Easy
Difficult
Medium
Difficult
Easy
Medium
Easy
Easy
Mediumt
Medium
Easy
Medium
Difficult
Easy
Medium
Easy
Difficult
Easy
Easy
SPECIES
GRN
WGT
lbs/cord
DRY
WGT
lbs/cord
HEAT/
CORD
1000 BTUs
EASE OF
SPLITTING
Excellent
Slight
Slight
Good
Slight
Slight
Slight
Bad
Excellent
Good
Slight
Slight
Good
Good
Fair
Slight
Slight
Excellent
Excellent
Slight
Slight
Excellent
Slight
Good
Good
Good
Good
Good
Good
Excellent
Good
Good
Good
Excellent
Slight
Slight
Good
Slight
Good
Good
Good
Poor
Good
Poor
Poor
Good
Excellent
Good
Good
Fair
Excellent
Excellent
Good
Poor
Good
Excellent
Excellent
Excellent
Excellent
Poor
Excellent
Excellent
Excellent
Excellent
Excellent
Excellent
Excellent
Excellent
Poor
Poor
Fair
Poor
Poor
Good
Good
Poor
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Few
Many
Few
Few
Few
Many
Few
Few
Few
Many
Few
Many
Many
Many
Many
Few
Few
Few
SMOKE
SPARKS
COALS
Excellent
Excellent
Excellent
Fair
Fair
Fair
Fair
Fair
Good
Good
Fair
Good
Fair
Good
Fair
Fair
Good
Excellent
Excellent
Excellent
Excellent
Fair
Excellent
Excellent
Fair
Excellent
Excellent
Excellent
Excellent
Excellent
Fair
Fair
Fair
Fair
Fair
Good
Excellent
Poor
FRAGRANCE
OVERALL
QUALITY
