Using the right wood can quite possibly solve a smoky fireplace or wood stove problem

Know your wood

Species Characteristics

Firewood from different species or types of trees varies widely in heat content, burning characteristics and overall quality. Table I below presents several important burning characteristics for most species.

Green weight – A cord of freshly cut wood weighs this amount 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 it must use heat to boil off its water before it can burn. It also produces more smoke and creosote than dry wood. You should always purchase firewood dry or allow it 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 best 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. Whether this is desirable depends on the proportion of low-density hardwoods, such as cottonwood, included.

Table I also contains information on other characteristics that determine firewood quality. Ease of splitting is important because you usually must split larger pieces of wood for good drying and burning.

Fragrance and the tendency to smoke and spark matter most when you burn wood in a fireplace. Woods that spark or pop can throw embers out of an open fireplace and cause a fire danger. Conifers tend to do this more because of their high resin content.

Use woods that form coals in wood stoves because they let a fire burn effectively overnight.

TABLE I. Firewood Facts

The amount of heat per cord of dry wood is presented in Table I. The heat content shows as a percent of dry green ash, a common Nebraska firewood. Values above 100 signify a higher heat content than green ash and values below 100 a lower heat content.

Species	Weight (lbs./Cord)		Heat/ Cord (1,000 BTU’S)	% Green Ash	Ease of Splitting	Smoke	Sparks	Coals	Fragrance	Overall Quality
	Green	Dry
Apple	4850	3888	27.0	135	Medium	Low	Few	Good	Excellent	Excellent
Ash, Green	4184	2880	20.0	100	Easy	Low	Few	Good	Slight	Excellent
Ash, White	3952	3472	24.2	121	Medium	Low	Few	Good	Slight	Excellent
Basswood (Linden)	4404	1984	13.8	69	Easy	Medium	Few	Poor	Good	Fair
Birch, Paper	4312	2992	20.8	104	Medium	Medium	Few	Good	Slight	Fair
Boxelder	3589	2632	18.3	92	Difficult	Medium	Few	Poor	Slight	Fair
Buckeye, Ohio	4210	1984	13.8	69	Medium	Low	Few	Poor	Slight	Fair
Catalpa	4560	2360	16.4	82	Difficult	Medium	Few	Good	Bad	Fair
Cherry, Black	3696	2928	20.4	102	Easy	Low	Few	Excellent	Excellent	Good
Coffeetree, Kentucky	3872	3112	21.6	108	Medium	Low	Few	Good	Good	Good
Cottonwood	4640	2272	15.8	79	Easy	Medium	Few	Good	Slight	Fair
Douglas-Fir	3319	2970	20.7	103	Easy	High	Few	Fair	Slight	Good
Elm, American	4456	2872	20.0	100	Difficult	Medium	Few	Excellent	Good	Fair
Elm, Red	4800	3112	21.6	108	Easy	Medium	Few	Excellent	Good	Good
Elm, Siberian	3800	3020	20.9	105	Difficult	Medium	Few	Good	Fair	Fair
Fir, Concolor	3585	2104	14.6	73	Easy	Medium	Few	Poor	Slight	Fair
Hackberry	3984	3048	21.2	106	Easy	Low	Few	Good	Slight	Good
Hickory, Bitternut	5032	3832	26.7	134	Medium	Low	Few	Excellent	Excellent	Excellent
Hickory, Shagbark	5104	3952	27.5	138	Difficult	Low	Few	Excellent	Excellent	Excellent
Honeylocust	4640	3832	26.7	133	Easy	Low	Few	Excellent	Slight	Excellent
Ironwood	4590	4016	27.9	140	Difficult	Medium	Few	Excellent	Slight	Excellent
Juniper, Rocky Mountain	3535	3150	21.8	109	Medium	Medium	Many	Poor	Excellent	Fair
Locust, Black	4616	4016	27.9	140	Difficult	Low	Few	Excellent	Slight	Excellent
Maple, Other	4685	3680	25.5	128	Easy	Low	Few	Excellent	Good	Excellent
Maple, Silver	3904	2752	19.0	95	Medium	Low	Few	Excellent	Good	Fair
Mulberry	4712	3712	25.8	129	Easy	Medium	Many	Excellent	Good	Excellent
Oak, Bur	4960	3768	26.2	131	Easy	Low	Few	Excellent	Good	Excellent
Oak, Red	4888	3528	24.6	123	Medium	Low	Few	Excellent	Good	Excellent
Oak, White	5573	4200	29.1	146	Medium	Low	Few	Excellent	Good	Excellent
Osage-Orange	5120	4728	32.9	165	Easy	Low	Many	Excellent	Excellent	Excellent
Pine, Eastern White	2780	2250	15.6	78	Medium	Medium	Few	Poor	Good	Fair
Pine, Jack	3200	2488	17.2	86	Difficult	Low	Many	Poor	Good	Fair
Pine, Ponderosa	3600	2336	16.2	81	Easy	Medium	Many	Fair	Good	Fair
Redcedar, Eastern	2950	2632	18.2	91	Medium	Medium	Many	Poor	Excellent	Fair
Spruce	2800	2240	15.5	78	Easy	Medium	Many	Poor	Slight	Fair
Sycamore	5096	2808	19.5	98	Difficult	Medium	Few	Good	Slight	Good
Walnut, Black	4584	3192	22.2	111	Easy	Low	Few	Good	Good	Excellent
Willow	4320	2540	17.6	88	Easy	Low	Few	Poor	Slight	Poor

Nice chart found while visiting a University of Nebraska-Lincoln and the United States Department of Agriculture web site.

More Firewood Notes

Wood supply preparation

You should dry wood as much as possible before burning. Properly seasoned wood has about 7,700 BTU 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 you fell the tree when it is fully leafed out, let it lie until the leaves become crisp so they can draw out as much moisture as possible before you cut it further.

Cutting wood into firewood length and splitting it—especially pieces larger than 8 inches in diameter—greatly reduces drying time. Split wood before stacking it, as splitting is easiest when the wood is frozen or green. You must stack wood properly 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. Remember that the wood must lose all its water before it will burn. If you cut and properly store your wood 6 months to a year in advance, then the sun and wind will dry it 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 beat 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.

Notes: Oregon Department of Agriculture