A comprehensive review of existing and emerging drying technologies available worldwide was prepared by FPInnovations in 2011.
This study showed that progressive-type kilns are more energy-efficient and have a superior kiln uptime due to the continuous loading and unloading process. The progressive-type kilns used by the lumber industry have one to five chambers, can be loaded in a longitudinal or transversal orientation, and can move lumber incrementally in counterflow or uniflow direction. In uniflow designs, all drying parameters (temperature, relative humidity, and air velocity) can be controlled in all zones. In most counterflow designs, only the temperature in the middle chamber and air velocity in all chambers can be independently controlled.