to solar kiln dry your lumber
Well, I could go into a really long speech about
designing and building your own solar kiln. Then an even longer
speech about the actual drying process. But there are more in depth
articles already on the internet written by experts in the lumber
industry. So I will just give you a quick overview and point the
way to everything you need to know about solar kilns, solar kiln
plans, and the process of solar kiln drying. Enjoy!
Here are my views on solar kilns.
1. They are extremely easy to operate with out messing
up your lumber. If you understand the principles of drying lumber.
2. They are extremely cheap to build and operate.
I have about $400 into the construction of mine. The operating
costs are only the electric that is used to run the fans for air
3. The process of heating during the day and the
cooling at night, results in minimal stresses in the lumber. Drying
to fast and to harsh will result in case hardening, checks, splits,
and warp in the lumber. The solar kiln minimizes this, just by
the way it works.
4. You can buy rough-cut green lumber from sawmills
for a fraction of the cost of surfaced and dryed lumber from a
distributor. So, you can buy cheap lumber, dry it yourself and
save your money for more shop
5. The only bad thing about solar kilns is that you
have to wait for your lumber to dry, instead of buying dryed lumber
right when you need it.
Here is the quick explanation of building a solar
kiln. If you want to go way in depth in solar kilns, then read
the articles provided in the links. But for you impatient guys,
I give you the jist of it.
The main things to do are,
1. Make sure the roof faces south for us in the Northern
2. Make sure the walls and floor are insulated very
well and very complete. You need the high temps during the day.
3. Use a good glazing for the roof. A non UV blocking
transparent material is what is needed. Corrugated Poly carbonate
from a green house supply company is the best thing to use, but
even plastic sheeting will work for a short time.
The first things to consider when getting ready to
build your solar kiln are where are you gonna put it, and how much
lumber do you want to dry at a time?
For a small solar kiln, that will hold 100-250bft
of lumber, you will need an area approximately 5'+ wide and up
to 12-16' long, just for your kiln to sit. And if you live in the
northern hemisphere, you will need an un-obstructed exposure to
the south, and visa-versa for the southern hemisphere.
The roof of the kiln will be covered with a "glazing" (poly
carbonate green house panels are best for a roof, but anything
transparent that will allow the UV rays to penetrate into the kiln
will work fine.) I used painter's plastic sheeting from Home depot
and it worked fine for a summer, then the UV rays had broken it
down and it began to crack and rip.
The roof should be pitched at roughly the same angle
as your latitude, I went 45 degrees here in NY, and my Lat. is
about 47, and it worked fine.
The floor of the kiln can be a concrete pad or a
regular joist type floor. When I built my solar kiln, I laid two
white oak 4"x6"x8' beams on the ground and leveled them.
I built my kiln on skids so that I could move it, if I ever needed
too. I then laid a painted sheet of 3/4" plywood on top of
the skids and then put 2"x6" floor joists down and insulated
between them. Then another piece of 3/4" plywood, painted
with aluminum roofing paint or something else to seal it and keep
the moisture out, is laid on top of the joists.
After the floor is down, you can begin erecting the
walls. I used 2"x4"s for the studs and again, insulate
well. Then paint all exposed surfaces inside the kiln, flat black
for maximum heat absorption. I used the first design shown here.
You need to leave two vent openings at the top of the back wall
and two at the bottom (approximately 1' square each). Then cover
them with screen to keep pests out. Then build some doors to close
off the air flow into the vents went needed.
*NOTE* I built it like it is shown, with the door
on the end. This makes it hard to load and unload the kiln. I had
to build a small cart and platform, so I could pile the lumber
on the cart and then just push the whole pile into the kiln. If
you do not want to do this, I recommend putting the door on the
back wall instead.
Now you need to mount the circulation fans in the
top of the kiln. I used metal attic fans from Home Depot, you just
have to remember that the temperatures in the kiln can reach up
to 200+ degrees in the peak during the day, so you need fans that
won't melt. They will suck in fresh air from the top vents and
blow the air down the roof slope and through the stickered lumber
pile, and finally out the bottom vents. Must of the time the vents
will be closed and the fans will just circulate the air through
the lumber pile.
After roughly a month and a half in the summertime,
your lumber will be dryed. For more in depth information refer
to the following articles. They will explain every little detail
you could imagine.
Great information and many different designs
Kiln Designs 1 -- Solar Heated, Lumber Dry Kiln Designs - Part
Kiln Designs 2 -- Solar Heated, Lumber Dry Kiln Designs - Part
Kiln Designs 3 -- Solar Heated, Lumber Dry Kiln Designs - Part
Kiln Designs 4 -- Solar Heated, Lumber Dry Kiln Designs - Part
Other sites about drying lumber
Drying: An Overview of Current Processes pdf (Excellent
CHECKLIST FOR DRYING SMALL AMOUNTS OF LUMBER pdf
With Wood I. Home Drying Lumber
SEASONING IN AUSTRALIA
long article on drying. I think you need to be a rocket scientist
to understand it. But just incase...here it is anyway. pdf
(long download time)