How to Get the Best Firewood for Clean and Affordable Energy

Enlarge Image Image Gallery A power log splitter can give your body a break as you prepare your firewood supply. ILLUSTRATION: ELAYNE SEARS

Firewood is better than money in the bank. It’s the tangible result of your labor, and it represents warmth and security through winter. If you know how to dry firewood properly, wood heat can be a clean, renewable energy that’s more accessible than solar or wind.

The three essential ingredients for efficient and environmentally appropriate wood heating are good stove technology, good fire-building techniques and good fuel. We’ve covered the first two topics in the past (see “Resources” at the end of this article). Now let’s look at what you need to know to have the best firewood.

Knowing how to dry firewood correctly is essential: Every serious wood burner must understand that wood dries slowly. Good firewood should have a moisture content between 15 and 20 percent, and it takes a long time for newly processed wood to dry to that level because the native moisture content of trees ranges from 30 to 50 percent. The efficiency losses resulting from burning wet wood can be as much as 30 percent, so drying firewood properly prevents a lot of wasted wood and results in wood that burns much more cleanly!

Here is a one-sentence prescription for good firewood: Logs should be cut to the correct length, split to the right size range for your heater, and stacked off of the ground in single rows in the open in early spring to be ready for burning in fall. 

However, hard species such as oak and hickory usually take longer than a summer to dry. Bigger chunks of firewood dry more slowly, and if you live in a damp climate, your wood will take longer to dry. If you don’t have an open, sunny location to stack your wood, it may take more than the summer to dry. Unless your conditions for drying firewood are optimal, you should prepare your firewood a year ahead. 

How to Dry Firewood: The Basics

Firewood that isn’t dry is slow to ignite. It smokes and smolders in the fire, causing both indoor and outdoor air pollution and leaving creosote deposits in the chimney. But that’s not all.

It takes a lot of energy to heat and vaporize the water in wet wood. Up to 15 percent of the energy content of green wood can be consumed turning water into steam and superheating it to the combustion temperature. Wet wood is so reluctant to burn that part of its potential heat energy is wasted as smoke, and it creates a sluggish fire that will smolder and make little heat unless the air control is left wide open. But an open air control will cause much of the heat produced to be rinsed out of the firebox and right up the chimney by such a high airflow rate.

In contrast, properly seasoned wood lights easily, burns cleanly and efficiently, and will continue to flame even if the air control is turned down for an extended burn.