My first Solar Kiln!

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Project by Firewood20 posted 12-22-2011 07:23 AM 5023 views 9 times favorited 10 comments Add to Favorites Watch

A buddy and myself built this solar kiln about 6-8 months ago have yet to use it… We did a lot of research on these things and had fun building it.(hope we did it right) We first milled a walnut tree last year and air dried it… which took a long time and warped quite a bit(we lost a lot of bdft) That’s what got us to believe we could speed the drying time up and control the RH with a kiln. Instead of paying someone to do it for us we used almost all recycled lumber and plywood and only bought a attic fan, wireless thermometer/RH, and the polycarbonate top(we first used painter’s plastic but that didn’t even last this last summer. For example how hot it got in there… 80F partly cloudy day here on the central coast california(this last summer) it was 130F inside, we still need to find the average for the different times of the year around here so we can set the fan to recirculate the air over the lumber every so often in the day. I will update with inside pictures but it still needs more black paint inside to retain heat. The approx size is 4’x8’x6.5’. and the slope of the roof is exact correlation to the latitude we fall at(it matters). Also the direction the roof faces(south facing) The unpainted board on the side is only to cover a vent that we are making sliding doors for to control air flow in and out, that are located on the sides and rear of the kiln.

-- Dustin, Central Coast California

10 comments so far

View WoodSparky's profile


200 posts in 3126 days

#1 posted 12-22-2011 12:10 PM

Looks good. In fact it looks like the one I had built a few years ago. I was one a job site, were the customer
had a Oak tree dropped a few years prier. The 24” diameter x 6ft logs were left behind by the buddy who had cut the tree down. The customer wanted the logs gone, and I wanted the wood. After a couple of nights and weekends of cutting with my chainsaw mill, I had a nice stack of Red Oak sitting in the middle of my garage. The pile of wood was like a massive speed bump slowing my use of the garage. This lead me to
build a solar kilm from drawings and plans off the Web.
This worked out great. Freed my garage up and helped speed up the drying of the wood.
One note of caution,watch your temps and air flow. I had lost some wood from a very green Oak tree that had later milled and loaded into the Kiln. My lack of attention during a couple hot summer day had turn part of the load into good firewood.

-- So Many tools, So little time

View shipwright's profile


7992 posts in 2822 days

#2 posted 12-22-2011 05:28 PM

I think these all look the same. They aren’t pretty but they work. Mine is made of left over OSB and 4mil plastic (Vancouver Island doesn’t have California’s sun intensity) and I’ve dried lots of wood in it. The one caution I would give from my learning experience is to make sure that if you aren’t drying the amount of stock recommended for the collector area you will have to reduce the collector area correspondingly by covering some of it. If not you will dry too fast in the critical initial stages. This is not a good thing.
Good luck. I think you’re going to love it.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees.

View B13's profile


463 posts in 2717 days

#3 posted 12-22-2011 06:08 PM

That’s cool! you could make a windmill from a car altanator Invert frow 12v to 120 for your fan.

View Milo's profile


869 posts in 3343 days

#4 posted 12-22-2011 08:11 PM

Ah, that is so cool… I am so jealous! Good job & good luck with the kiln!

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

View Dennisgrosen's profile


10880 posts in 3139 days

#5 posted 12-22-2011 10:47 PM

you just have to let the thermometer controlling the fan/fans
to control the humidity and heat in the killn


View lightweightladylefty's profile


3241 posts in 3736 days

#6 posted 12-23-2011 06:10 AM

We couldn’t wait to use a kiln! Wish we had one!

A question: How do you access the kiln? All the plans that we have seen have doors either on both ends or in the back. Since it is placed in the corner of the fence, we wondered how it is accessed?

We’ve had pretty good success with air-drying our lumber, but have learned that precise stickering and ample weight is necessary to keep the wood from twisting. It also makes a huge difference if there is any stress on the wood (growth rings not centered). It’s really quite a science to get it right. We doubt that we ever will ;-(, but it’s fun trying.

We can’t wait to hear how your kiln works out . . . so get a load in there soon ;-) !


-- Jesus is the ONLY reason for ANY season.

View Don Carrier's profile

Don Carrier

114 posts in 2400 days

#7 posted 12-23-2011 02:48 PM

I helped build a couple for a friend last year and they worked great. One thing we ended up doing was purchasing small temperature controlled attic fans. These seem to stabilize the temperature and prevent wild swings. My brother is an a/c tech and he got the fans for about $60.00 each. We hope to convert the fans to solar(electric) this coming year.

-- Don

View douglbe's profile


369 posts in 3985 days

#8 posted 12-23-2011 03:18 PM

I also built a similar solar kiln two years ago and have put about 2,000 bd. ft. through it. Any lumber I put in, I let air dry for a couple of months first, this helps prevent more warping and cupping when in the kiln. I dried walnut, hard maple, white ash, cherry, and basswood and I have had super results, very little warping and cupping. Most of the white ash, maple, and bass wood boards are really flat and straight, then again these came from larger diameter trees and very few knots. Same as Don Carrier, I use a temperature controlled attic fan and I have great results. Have fun, you’ll get fantastic wood.

-- Doug, Reed City, Michigan

View Firewood20's profile


43 posts in 2712 days

#9 posted 12-23-2011 07:42 PM

Here’s a youtube video link that I basically followed… guys are very knowledgeable. Inside this one is exactly what mine looks like… however my vents are a little different and I don’t have a base of DG under the kiln. If you are just starting out… watch this!
Thanks everyone for looking at my project. I can’t get enough of this site, great inspirations. While at work here Fire Station, I often check it on my down time or during lunch. It’s addicting.

-- Dustin, Central Coast California

View AZWoody's profile


1346 posts in 1248 days

#10 posted 04-02-2015 07:04 PM

That’s is definitely on one of my to do lists.

I have been air drying all my slabs but I need to speed up the process and also have some baddies inside some of the logs that I need to get rid of.

My worry is that being in AZ, it will be too hot. It can get 115f here easily in the summer and so I really do worry about hardcasing. I think the key is not opening the vents very much and just letting the moisture seep out on it’s own.

I will do some with air drying a little first, then some directly to the kiln. Eucalyptus can warp very, very much if not weighted down, and even then it’s been known to knock off my weights from the top.
Maybe, in the kiln with high humidity from a closed vent, it will warp less. Time will tell.

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