QHT Boiler manual Wood Burning, Overview, Selecting Your Wood, Cutting and Drying Your Own Wood

WOOD BURNING

Overview

Burn dry and well-seasoned hardwood with a moisture content of 20% or less. Wood must be seasoned at least six months; however, it is preferable to season it for a year to eighteen months. Seasoned wood will not only reduce creosote but will also produce more heat. Some sea- soned hardwoods will yield 20-25% more heat. Wood-burners who ignore this advice are likely to have dirty chimneys and inadequate performance from their boilers.

Theoretically, there are about 8,600 BTU available as heat from each pound of wood. It takes about 1,000 BTU to evaporate each pound of moisture from a log. The wetter the wood, the more energy it takes to get the moisture out of the firewood resulting in less energy to heat your home. In addition, green wood usually burns at a low temperature, robbing you of even more heat in the form of unburned chemicals and gases that it sends up the chimney. The moral is: do not burn green wood.

Selecting Your Wood

If you buy green wood, season it before using. With some experience, you can spot green wood easily. It is heavier and it looks different. Seasoned wood will often show cracks radiating outward from the heartwood toward the bark, like wheel spokes. Green wood will not show this pattern of cracks.

You get roughly the same amount of heat from a pound of equivalently dry wood no matter what species of tree it comes from. But wood is not sold by the pound; it is sold by the cord i.e. by volume. Therefore, the dense heavy woods are the ones to buy, the ones that give you more pounds per cord. A cord of wood measures 4 feet x 4 feet x 8 feet. A cord of 4-foot logs thus stacked occupies 128 cubic feet and contains about 80 cubic feet of solid wood, with the rest be- ing air space between the logs. If you buy a cord of wood, cut it to length and split it, you will find it does not occupy 128 cubic feet when stacked. You have not necessarily been cheated. A cord cut to length and split packs more tightly thereby occupying less space. Often the best time to buy wood is in late winter or early spring. Green wood can sometimes be purchased at low prices in spring or early summer.

Cutting and Drying Your Own Wood

A good time to cut your own wood is in the late winter or early spring, as soon as the woods are free of snow. Then hold the wood for use in 18 months. If you cut trees in the spring or sum- mer, let them lie a while until the leaves wither. The leaves will draw moisture from the wood; drying it more quickly than if you limbed the tree immediately.

If you want your wood to dry as quickly as possible, cut it to length and split it. Stack it where the air can move through the pile and shelter it from the weather. A wood shed with air vents in the sidewalls, like a tobacco-drying barn, is effective.

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