Air Drying vs. Kiln Drying: Which is Best?

Updated: Sep 16, 2020

Expense, convenience, timing: there are a lot of factors to consider when choosing which lumber drying method is right for you.  We compare the benefits and drawbacks of air drying, traditional kiln drying, and vacuum kiln drying lumber.

Drying lumber can be a lengthy, risky, and expensive process, but it doesn't have to be.  Advancements in wood drying technology have reduced the time it takes, lowered the risks of damaging your lumber, and significantly lessened associated costs.  We will explore air drying, kiln drying, and vacuum kiln drying below:

1) Traditionally once lumber is milled into its rough dimensions, it is placed on what are known as stickers, 1”-1” wood sticks, which are placed between the layers of lumber. This allows for air to flow over the lumber surfaces and reduce moisture. Typically this takes 1 year per inch of thickness to reduce the moisture from fresh cut or “Green” lumber to 7% which is ideal for making furniture. 

Vacuum kilns reduce the time from potentially years to 2-4 weeks when drying lumber from “Green” to 7%. Some people may be misled by trying to save money by air drying lumber. It actually comes with many hidden costs. For example; there is a cost for storage, a cost to ultimately drying the lumber, so you can kill any bugs in the wood. This cost averages between $.35-$.60 per board foot, plus the costs of storage, overhead, insurance, etc.  Vacuum kiln drying costs from $1-$2 per board foot, depending on the thickness. Plus, rather than paying for years of storage your lumber is ready within only a few weeks.

2) You can air dry lumber wherever allowed by law and typically there are lumber drying services in most major cities. Vacuum kiln drying is not as readily available, so if you have one in an area near you, take advantage of the time saver and technology.  In many cases, it may even be worth driving to a different city to dry your lumber in a vacuum kiln.

3) The effectiveness of each drying method depends on the proprietor, the equipment, the lumber and the time frame. Dehumidification kilns typically will have 15-20% degrade to the lumber in the drying process. Whereas, the vacuum kiln will have less than 2% degrade. With less degrade and shorter drying time, the vacuum kiln is much more effective.

4) The integrity of the wood can be compromised when air drying due to bacteria, the weather, insects or by improperly stickering or storing of the lumber. The only way to compromise the lumber in a vacuum kiln is to dry it too hot or too quickly. This can cause checking, cupping, or warping to the lumber. However, as long as the proprietor of the vacuum kiln is experienced, it is very unlikely that any issues will occur.

Interested in learning more about our vacuum kiln or lumber drying process?  Please give us a call at (513) 581-0361 or use the form on our Contact Us page to reach out.

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