Design and Operation of a Solar-Heated Dry Kiln

Wood Products January 12, 2015 Print Friendly and PDF

Brian Bond, Assistant Professor and Extension Specialist, Department of Wood Science and Forest Products, Virginia Tech


Lumber is usually dried to a specific moisture content prior to further manufacturing or use. The amount of water in wood is usually expressed as moisture content and can be directly measured or calculated. The moisture content of wood is defined as the ratio of the weight of water in wood to the dry weight of the wood material. While lumber can be air-dried, the humidity in most localities prevents the lumber from reaching the moisture content required for the stability needed for interior use. A dry kiln is required to dry lumber to the necessary final moisture content and does so fairly rapidly. This publication discusses the design and operation of a solar-heated lumber dry kiln that is designed to be inexpensive to construct and simple to operate.

Virginia Tech Solar Kiln Design

The solar kiln described in this publication was designed, constructed, and tested at Virginia Tech. This design is based on 25 years of research and development on the solar drying of lumber in the United States and foreign countries. Previous versions of this kiln were designed to hold up to 2,000 board feet1 of lumber. Plans for the older and larger kiln are available for download at The version described here holds 750 to 1,000 board feet of lumber. The kiln dries a load of lumber in approximately one month of moderately sunny weather at its location in Blacksburg, VA.


Solar kiln dryer at Virginia Tech



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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.