Solar kiln alternatives

[Matt Krusen]

In the next few weeks I would like to construct an outbuilding for lumber drying and storage. I would love to build a small solar kiln but unfortunately my fiancé wants the "shed" out of the way behind the shop. That area really doesn't get much sun so I'm not sure the solar kiln idea is going to work. I'm looking for some alternative options. This is my first foray into milling and drying my own lumber so any help would be great! Thanks everyone.

[Jim Andrew]

Is the south wall of your shop available? Maybe you could build a lean-to shed on the south side and use some plastic covering and fans, along with a
dehumidifier. Just a dehumidifier in a room full of lumber will dry the lumber faster than drying outside, and when it is done, it is ready to build with immediately.
Your room or shed will have to be well sealed and insulated for any kind of drying to work well.

[Matt Krusen]

Any problems with a dehumidifier drying too quickly? Checking or anything? The south wall of the shop is my main wall so I won't be able to build anything there. I'll already be building a 12'x12' (or larger) shed behind the shop and would love to be able to somehow configure it to dry/store lumber as well.

[John TenEyck]

Any problems with a dehumidifier drying too quickly? Checking or anything? The south wall of the shop is my main wall so I won't be able to build anything there. I'll already be building a 12'x12' (or larger) shed behind the shop and would love to be able to somehow configure it to dry/store lumber as well.

Yes, an uncontrolled dehumidifier is likely to dry the wood too quickly. With a simple control system, however, a dehumidification kiln is easy to build, safe, simple and cheap to operate, and yields very well dried lumber free from stress. I built one in my basement shop generally following the plans from an article in FWW in the Nov/Dec. issue 1991. Here's a picture with the door removed.

285429

It's big enough to hold about 275 BF. I first air dry the lumber that I mill outside until it's down to about 14% MC, as low as it will go in my area. From that point a full load takes about 10 - 12 days to dry to 6 - 8% in the kiln at a cost of less than $20. Happy to discuss further if you have an interest.

John

[Bradley Gray]

You might want to look into a dehumidification kiln system. A dehumidifier made for drying wood is made of stainless instead of aluminum to resist acid from oaks and includes a heater and a controller. I have a system made by Ebac (English) that I have used for over 25 years - still going strong. Nile is another mfg.

[Jim Andrew]

You can read lots of threads on solar kilns at forestryforum.com There are guys there who use the small room dehumidifiers in their solar kilns to dry lumber. The solar provides the heat, and the dehumidifier removes the moisture from the kiln. You have to sticker the lumber and use fans to circulate the air between the boards.

[Larry Edgerton]

Logosol makes a reasonable priced unit for about $1600. ForestryForum has used ones for sale as does Sawmill Exchange.

[Yonak Hawkins]

Matt, this situation is rife with nuance, definition framing and potential pitfalls. It's a classic case of want vs. need, looks vs. practicality, Venus vs. Mars. You have to make your fiancé want it or, at least, not hate it. Obviously a solar kiln is not going to work where the sun don't shine and that's exactly where your fiancé will suggest you put this "monstrosity" if it upsets her sense of decor.

You have to ask yourself if that's all you want .. a place to dry wood .. or will it also store wood in perpetuity. If the main purpose is storage (of not only wood, but bicycles, camping gear, lawn mower, her stuff - that's a plus) maybe it can be around back and a temporary kiln, solar or otherwise, for only those times when you have green wood (which, for me, amounts to about once a year, for a few weeks) could be constructed and removed before her mother comes over.

If you want a permanent solar kiln there are angles you could pursue and still maintain peace on the home front. You could build it out back and put a discrete collector in a place that gets sunshine but may not be obtrusive such as, maybe, on top of your house or poking up above your house gutter line, somehow, but still behind the house. The problem with that is you'd have to insulate the full length of the ducting and, if the collector is a long way from the kiln, you'd lose a good bit of heat. You could combine passive solar with a dehumidifier.

Maybe a solar kiln, low to the ground (could you make it with a lift-off top instead of a walk-in building ?) that doubles as a greenhouse where your fiancé could prepare seedlings for spring planting -- it could never hurt for her to get something out of it, too (if you also did the planting, that would be a plus for your venture). Maybe it could be some kind of structure that can be modified to not look like a kiln .. could it be partially buried or look like a child's playhouse or a doghouse or decorative feature somehow ? Could you use the attic space above the garage as the kiln, with a system devised to move the lumber in and out, or the collector on garage roof with the shed built behind it ? Just some thoughts... It makes everyone's lives easier when there's harmony in the household .. believe me, I've learned the hard way.

[Bob Falk]

Here is a dehumidification kiln design from the Forest Products Lab. Rather elaborate IMHO, but I have talked to the authors and they told me you can make an even simpler basement or shop wood drier by constructing a 2x4 wood-framed box wrapped with visqueen plastic. Dehumidifier, fan, etc. and other controls basically the same.

http://www.fpl.fs.fed.us/products/publications/specific_pub.php?posting_id=18087&header_id=p

American woodworker also did an article and Woodweb has some discussion:

http://www.scribd.com/doc/23271563/American-Woodworker-094-06-2002

http://www.woodweb.com/knowledge_base/HomeBuilt_Dehumidification_Kilns.html

[John TenEyck]

Here is a dehumidification kiln design from the Forest Products Lab. Rather elaborate IMHO, but I have talked to the authors and they told me you can make an even simpler basement or shop wood drier by constructing a 2x4 wood-framed box wrapped with visqueen plastic. Dehumidifier, fan, etc. and other controls basically the same.

http://www.fpl.fs.fed.us/products/publications/specific_pub.php?posting_id=18087&header_id=p

American woodworker also did an article and Woodweb has some discussion:

http://www.scribd.com/doc/23271563/American-Woodworker-094-06-2002

http://www.woodweb.com/knowledge_base/HomeBuilt_Dehumidification_Kilns.html

The fpl link shows a nice looking but space inefficient kiln. I have no clue why they choose to blow all that air around the stack of wood rather than through it. In the design I followed the air blows through the stack which allows you to fill the kiln floor to ceiling and tight against the plenum wall, with only a small space at the front to act as a return to the fan inlet. The AW link shows a design similar in concept to mine.

John

[Richard Coers]

You can put air solar collectors on the roof of the garage or draw the hot air from the attic of the garage/and or house into an insulated box. Easy to get 120+ degree air from an attic in the summer in the midwest.