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Solar Kiln from Storm Smashed Greenhouse11/11
My lovely bride has expressed displeasure at our back porch being filled with green cherry, black walnut, ash, and locust covered in those ugly blue tarps is how she puts it. I told her that I didn't have anywhere else to put it. I think she is missing her chats with lady friends out there.
Well, that might have changed. My buddy Josh, a retired veteran too, He collects scrap for extra money, found a polycarbonate green house that someone was throwing away because one of the lower sidewalls got smashed. He thought that I might be able use it and/or repair it. He has heard my wife say that she wants a green house. I think I might be able to turn it into a solar kiln for use now and later the wife can use it as a greenhouse in the early spring. Then I can turn it back into a kiln for the summer and fall. Kind of double duty and I can say that it is a greenhouse for her.
My plan is to attach it on the South side of my reffer shipping container. We have all the frame pieces of the greenhouse and they measure about 18 feet long by 8 feet wide when I put the two halves side by side or is it end to end. It is about 7' at the roof peak, With planned floor it will line up with the top of the shipping container. It is 24" between all the frame pieces except the door pieces. There is a 30" door in each end. The frames are made from steel painted black.
I was thinking of a 2x4 24":OC frame attached to the side of the shipping container then some sheet material for the back wall. I was going to insulate this with the pink stuff. Then attach the two greenhouse halves at each stud with a screw thru the frame. I have some deck piers blocks leftover from placing the shipping container so we can build a 2x6 floor 12" OC to get the lumber up off the ground. I would like to do 24"OC but don't think that the span would support the wood pile. I was thinking just laying down shipping pallets over the floor frame for the floor I was going to put a sheet of 6mil plastic over the frame as a moisture barrier. I have quite a pile of AC2 pressure treated lumber from dumpster retrieval at construction sites.
Josh pointed out that I don't need more material to cover the busted out part I can use the material from the two inside ends to fill in the missing poly. That way we can get through the whole structure not just the small door in the middle.
It has two solar powered fans, one on each end. I was going to remove them and fill in the openings. I figure if I put them on the frame pieces in the center of the greenhouse in the sun that they would move the air around inside the kiln.
To help hold the heat in we are going to cover the back wall with foil backed rigid foam to reflect the heat back at the lumber stack that I want to dry not transferring the heat to the lumber stored in the shipping container. This insulation had been on the walls of my shop but they took it out when they filled the blocks with foam. It 4" thick and is R-26. I was going to cover the floor frame with 6 mil plastic under the pallets to keep moisture from coming in from the ground. I don't think that I need any vents that enough air will get in and out by my sloppy construction. I do have some leftover black interior trim paint that I could paint the floor black with it or is the black plastic sheeting enough.
It was a pretty nicely built green house. Even after being tossed into the bed of a pickup and hauled around the door works just fine. All the panels are double layered polycarbonate and sealed. It has roof windows but I don't plan on using them.
So now the question that I have are these...
Will a solar kiln work over the winter in IL or should I wait until spring to set it up?
I have more umber on the back porch than will fit, is there a way of condensing it? My stack on the back porch is 13'x36-38'x6-8'. It is about half cherry, a quarter black walnut, and the rest locust, ash, and maple. The pieces are about 9/4 to some 12/4 with the bark still on them.
Also anyone ever painted a shipping container? I am told that we are painting it TARDIS blue. I thought that I could powerwash it then attack it with the Wagner Power Sprayer. Sound doable or think again?
Josh wants to trade for me putting a SSD drive into his old laptop. I told him that I would put the drive in for nothing. The drive is a 40GB that I had been using for LAN gaming. He has also offered to help with greenhouse/kiln if I feed him, He said that it would be more fun than channel surfing.
I also posted this over at wood talk sorry if double post...
Thank you for your advice,,,,
For effective solar drying, you need about one square foot of collector for every 10 bf of lumber.
Will a solar kiln work over the winter in IL or should I wait until spring to set it up? Northern IL...no, not much. Southern IL, yes, unless the winter is really cold.
How much of a air gap do I need to leave around the lumber stack? One foot at least on the edges.
Is there a limit on how high we stack the lumber? The higher the stack, the more chance it will become unstable and tip over. It depends on pile width, but in general twenty layers or about three feet high and then you need a 4x4 crosser or bolster for stabilization.
I don't know if it is today's rainy weather or what but when I checked with the moisture meter the green stuff was 38-46%. I assume you used a moisture meter. They are not reliable above 28% MC, so you really do not know how wet the lumber is.
I have more umber on the back porch than will fit, is there a way of condensing it? You need at least 12" on each side of the stack. The lumber needs to be on 3/4" thick stickers.
Also anyone ever painted a shipping container? The darker the color, the kore solar heating you will get. A dark roof is especially beneficial.
Thank you Gene,
I am in central Ill, according to everything we are in for a bad winter. I am going to go ahead and set the greenhouse up. After talking to the person that has a solar kiln 60 miles south of me. He has a Virgina Tech design solar kiln for about 1000bf. I am going put the R-26 foam between the floor joists. He also suggested putting it into the hip wall while using it as a kiln. He also said that I should get some lumber drying cart made or bought. He recommended cheapo fans in the front and ends of the stacks. He also said to paint the floor and back wall with black aluminium paint. He also said that I needed a moisture barrier between the back wall and the shipping container wall. Even if it doesn't work as a kiln it will get the wood off the back porch and make the wife happy.
Gene do you agree with all of his recommendations?
You bet. You will find most of them or their concepts in the VT plans.
We have started this morning about 6 am. I have been using my Japanese style saw to cut the foam down to fit between the 2x6 joist. We are moving along quickly. I am tacking things together with framing nailer and Josh is go after me with screws. We have the floor platform built.
Cold as can be here today. Actually seeing snow flakes. Eager to get the frame up to get out of the wind.
Will let you know how it goes along. Also decide to use up decking board for the floor instead of pallets. Would be nicer for the greenhouse uses.
It has been up for about a month now. The temp inside the kiln goes to about 50-60ºF above the outside temp and is a complete sauna with all the humidity coming off the green lumber. On sunny days the green house panes stay clear but on cloudy days they fog over. The panes have a gap between them so that air gets heated from the floor up to the peak were it enters the greenhouse/kiln. Today we got to 37ºF for a outside high and the greenhouse/kiln got to 81ºF with it being partly cloudy. I filled the floor with R26 foam stack on itself between 2x6" joist. We used sheets of 6 mil plastic to line the floor and back wall. With the run off going to the front edge and out a tube. The fans do a good job of moving around the air. Fresh air comes in the gaps at ground level between the poly-carbonate panes. They then get heated by the sun and enter the kiln at the peak next to the back wall. The temp control system closes these gaps if it is below the set temp. I have the bypass temp set at 50ºF. So from about 7 pm to 8 am the kiln is recirculating. When the humidity hits the poly-carbonate panes it condenses and runs to the floor and out the lowest corner where I installed a drain after having condensation pool here. I have ducked into the kiln during the day to warm up while doing outside tasks and found it very nice place to warm up. I have gotten a good amount of wood into it. I have a pile with ¾" sticks that is 18' long by 7' front to back with it sloping front to back from a front face of 4' to 8' near the back wall. I have put a 20" box fan every 3' along the back wall hanging from the roof. They are blowing towards the front panes. This way the air currents pick up humidity from the wood and carry it to the cooler poly-carbonate to condense and remove it from the air inside the kiln.
I will measure the moisture content of some pieces after it has been a week. When it was colder I could see the frozen condensation outside the drain tube. I am hoping that it will take 3-5 months during the winter to dry the lumber. I am going to have to make some carts for moving the lumber in and out as that is a all day affair.
Sorry about rambling post but thought people would like to know how things were going.