There are many benefits to drying your own lumber. First of all, properly dried lumber typically sells for more than 30 percent higher than prices for green lumber.
Kiln-dried lumber is also better to work with: it machines better, has more holding power when glued together, finishes easier, and nails and screws have higher holding power in kiln-dried lumber. In addition, dry lumber weighs more than 50 percent less than green lumber and is more than twice as strong and stiff.
Plus, lumber dried to below 22 percent moisture content has no risk of developing fungal stain, decay, mold, or rot, while kiln-drying kills infestations, hardens pitch, preserves color, and controls shrinkage.
Lumber that is not dried under controlled conditions in a kiln is prone to warping and other degrade that diminishes its selling price and workability.
Air-drying lumber — relying on the sun and a natural breeze — has numerous drawbacks. Air-drying poses real problems with damage and degrade and is often the most expensive way to dry lumber once you include interest on material investment, labor, land costs, and especially loss from lumber degrade. In addition, for lumber that will be used in furniture or some other finished product that requires drying to 6-8 percent moisture content, air-drying is not sufficient.
Kiln-drying, with the lumber placed in a chamber, allows control of air flow, temperature, and humidity in order to dry the wood as rapidly as possible without increasing defects. There are several types of kilns. However, solar kilns and dehumidification kilns provide many benefits with only a low investment.
Wood-Mizer offers kits for solar kilns and dehumidification kilns to make drying lumber easy, affordable, and profitable for virtually any size company.
Solar kilns generally rely on some type of solar collector to provide the heat energy that evaporates the water in the lumber. Yet, drying times for a solar kiln still depend on the weather, so they are unpredictable. However, a solar kiln is very affordable for entry-level drying operations and often will pay for itself after drying just three or four loads of lumber.
A dehumidification kiln uses a heat pump system to produce heat and remove the water from lumber. One primary advantage of this type of system is that it recycles heat continuously instead of venting away heated air like a conventional kiln; a dehumidification kiln therefore is more energy efficient, and operating costs usually are lower.
In a dehumidification kiln, heated air is circulated over the lumber while separate circulating fans evaporate the water contained in the wood. The hot, moist air then is cooled at a cold refrigeration coil, and the heat removed from the air is immediately used by the system to heat the air back up again.
Dehumidification kilns are very easy to operate and are popular with beginning lumber dryers as well as experienced operators who want a system that requires minimum attention yet produces kiln-dried lumber with zero defects. Dehumidification kilns are more expensive than solar kilns, but they can provide top quality kiln-dried lumber year-round regardless of the weather. Also, the cost of operating a dehumidification kiln compared to the value added by drying lumber often makes the return on investment nearly 20 percent or more.
Wood-Mizer offers dehumidification and solar kiln kits with capacities ranging from 300 to 35,000 board feet. For more information, visit www.woodmizer.com/kilns.
(Editor’s Note: The above information is based on the Wood-Mizer Introduction to Kiln Drying Guide. The complete guide is available as a free download at www.woodmizer.com/kilns.)