Dehumidifier Kiln

Well, after much thought, research, and stalling, I finally built a dehumidification kiln.

You see, the last time I cut trees was last Spring. That lumber has been stacked and air-drying for over a year now. I recently finished off my supply of oak, and now I’m starting to get itchy. Another year in the shop to air-dry further? You gotta be kiddin’.

Being a small time sawdust maker and electron slayer, I probably could give in and go to the local hardwood lumber yard and (gulp) buy some lumber. There. I said it. Give me a moment while I go brush my tongue.

Buy lumber? You mean they sell it cut, dried, and ready to transform into what surely someday will be treasured antiques featured in the Carnegie Museum? What fun is that?

No, thank you. I prefer sweating. Swearing. Near-death experiences. To go to a lumber yard and buy ready-made lumber–wouldn’t that be like cheating on my trees? “Sorry guys, I found someone else. Smoother; drier; someone who doesn’t threaten my life by falling with tremendous force to the forest floor.” Just doesn’t seem right.

Moisture content, as I mentioned before, is my sparring partner when preparing to build. Not quite my nemesis, it’s more of a friendly bout.

When you design some of your projects, as most woodworkers do (you just can’t trust printed cut-lists), you always have to keep moisture content in mind. As hard as it is to believe, wood doesn’t die when you cut, dry, and murder millions of electrons on it. It continues to live on in the maddening movement that occurs with the change of the seasons, and with that, the relative humidity in the air. No, when designing furniture, you have to design with the idea that wood movement is inherent, inescapable, and capable of ripping your furniture to pieces.

Oh, yeah, the kiln.

Well, how can I get that beautiful stack of Cherry and Soft Maple out of the drying stack and into my shop–er, studio? (What a snooty word for “shop”.) I need to dry it further, and fast.

Daren Nelson, a woodworker over in Illinois, has plans on Ebay on how to build a nice, inexpensive dehumidifier kiln. **Alert** for those of you (all two or three of you) who read this for the humor and philosophical insight, I’m going into some nuts-and-bolts now.

The kiln is a simple box, airtight and insulated, that contains a small heat source, some fans, and a dehumidifier. Without putting you to sleep, I’ll just say that the initial heat source is turned on to get the kiln to temperature, while the fans and dehumidifier run all the time. The moisture is drawn from the wood by the heat, and the dehumidifier continuously draws the moisture from the air. When the kiln is up to temp, the heat source is turned off and the dehumidifier keeps the temps up to operating range.

Brilliant. Fantastical. Cheap. Did I say cheap? For fifty cents/boardfoot I can have my lumber dried at the (gulp) lumber yard. At home, I can dry it for as little as five or ten cents/boardfoot. In as little as two weeks. Sorry, I’m drooling. In two weeks I can start my merciless slaughter of millions of defenseless electrons. A blood-thirsty grin pasted on my maniacal face, dreaming of the new sideboard against the wall of my dining room. Well, maybe not millions of defenseless electrons. . . have I mentioned my handtool collection?

About Sam

Young, good-looking, manly--you get the picture. Novice woodworker with just too much rolling around upstairs to keep to myself. Random thoughts, philosophical questions, the occasional flash of insight or just dumb luck that needs to be shared with anyone who cares.
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3 Responses to Dehumidifier Kiln

  1. Sonny hart says:

    I am looking for Darens plans. He has cut links and not selling them anymore that I can find. Do you know where I can get a set of his plans?

    • Sam says:

      Hi Sonny,

      Daren is one fickle individual. You don’t really need plans to build a kiln, but I will help you out if I can. I’ve been toying with the idea of drawing plans up in Sketchup because so many people seem to want them.

      Really, you just need to decide how big you want it, get the lumber, and go to town. I built mine by building a bottom with a 2×4 frame and a piece of OSB nailed to it. I then built the sides and top the same way. I painted the interior with a good oil-based enamel (Rustoleum), screwed together the bottom, sides, back and top, and then attached the front with hinges on the top so I could lift the loading door up and out of the way. Caulk the inside to make it airtight, and you’re almost done. Decide how you want your D/H and fan to fit in there, and load it with lumber. It really is that easy. Most people just put the D/H on one end and the fan on the other.

      Daren’s plans really didn’t give much more info than that. You have to decide how you want to build it.

      I think I gave pretty much the same info in the post–you want to insulate the outside to make regulating temperature easier.

      If you have any more questions, or need more specifics, I’ll be happy to oblige.


      • Sonny hart says:

        Hi Sam,

        Sonny here. Thanks for responding and sorry for not responding back. I just actually found you again. I forgot to bookmark and could not remember the name.
        I am going to build a D/H kiln this fall. I just went out and cut up 13 walnut logs, 5 cherry, and some more maple I need to mill and dry.
        I need some advice on the actual dry info. Like: home depot has 3 differ sizes of D/H. What size do you have? Also you use lights to heat up then turn off. What temp do you stop at? 130 or so to kill bugs. You also said to put insulation on the outside? Are you just using rigid and take off if box gets to hot? How about just a vent or temp gauge that turns it off when it gets a certain temp?
        Any new tips on setting the louvers. Looks like they tapper as get to other side of the box?

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