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Building my first solar kiln

Started by etd66ss, June 14, 2021, 06:29:59 AM

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metalspinner

Unlike other forums, forestry forum members have a gallery in which you can organize and store your pictures. This also houses the pictures permanently so that threads like this will always contain the photos used to  aid the discussion. 
I have pictures in my gallery that go back 15 years?? I have long lost access to my original photo storage and appreciate that these are here. 
I do what the little voices in my wife's head tell me to do.

Larry

I built and operated a solar kiln for 12 years.  It did an excellent job and even had a picture in one of Dr. Gene's articles in Sawmill & Woodlot years ago.

I've also been involved with two other builds.  One guy did not use double glazing with disastrous results.  During cool and cold weather moisture would condense on the single glazing.  Than it would drip off onto the floor.  If he had not fixed it the whole floor would have rotted out.

Second thought is lumber from treated poles does not last any longer than untreated lumber.  It has the smell and color, but not enough preservative makes it through the outer few inches of the shell to do much good.  I did not use treated lumber for my floor joists and did not have any problem, but I had it elevated off the ground maybe a foot.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

etd66ss

Doubling up the glazing is not going to work for me, that would be over $1000 just for the glazing. I'm trying to make this thing out of sawn lumber and very limited purchased components.


It also seems like the Tuftex would be a nightmare to double layer with the way the joints overlap and how I'd have to make double sided closure strips with a jigsaw...

https://www.lowes.com/pd/Tuftex-Wood-Solid-Roof-Panel-Closure-Strip/3012462

Is this 6mm twin layer stuff what I should use?

https://www.lowes.com/pd/Tuftex-Multi-Wall-6mm-Panel-Clear-4-ft-x-8-ft-Corrugated-Polycarbonate-Plastic-Roof-Panel/1000689436

It doesn't seem as durable as the corrugated to me, and it only comes in 8ft long sheets, which means I'd have to have a roof overlap somewhere.

QuoteSecond thought is lumber from treated poles does not last any longer than untreated lumber.  It has the smell and color, but not enough preservative makes it through the outer few inches of the shell to do much good.  I did not use treated lumber for my floor joists and did not have any problem, but I had it elevated off the ground maybe a foot.

I'm using sawn creosote utility poles for the floor joists and rim boards.

EDIT: Found this place:

https://www.interstateplastics.com/Polycarbonate-Twinwall-Clear-Sheet-POLCE~~SW.php?kitoptionpk=197&src=adwordspla&thisisforcallrail=1&campaignid=225228743&adgroupid=37851262274&creative=153445283219&matchtype=&network=g&device=c&keyword=sheets-POLCESW-kits197&gclid=Cj0KCQjw5auGBhDEARIsAFyNm9Fa1Zo6h62CavAZdq8fHvPzeYlDnBP660EKndqbbi6vnU-NfIWsBa4aAjX7EALw_wcB

Anyone order from Interstate Plastics before?

Does the thickness of the twin wall matter? I imagine the farther apart the twin walls are, the higher the R-value of insulation. They have 6mm, 8mm, 10mm & 16mm, they also have triple wall, but that's $320 for one sheet...

etd66ss

Well, I just built up a cart of what I would need for the glazing:



 

Might have to rethink this solar kiln build. Thought it was going to be cheaper than this...

The whole reason I wanted to build a kiln was to saw and dry ~1000 bd-ft of 1x8 Scots pine to turn into T&G for the ceiling of my house build. As well as 6x10x24ft & 6x6x12ft beams from the same wood. Maybe I'm dreaming that a kiln + me felling the trees and milling the rough boards & timbers would be cheaper. I still need them finished into T&G and re-sawn beams. Though I was thinking I can re-saw the beams and sand them.

doc henderson

the original design is only 14 feet long if I recall.  you can build it with the corrugated stuff, but will not be as great in the winter compared to the summer.  but I think as long as you get a differential of 20 or 30 degrees inside vs outside, it will dry faster than air drying.  the big beams may do well just to be well covered and air dry down to 12 %.  
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

etd66ss

I might be money ahead to just air dry the beams as suggested and have the general contractor acquire the T&G for the ceiling, though I really wanted the look of Scots pine for the T&G vs the bland white pine available.

-or-

I build a 16ft Kiln and not try to kiln dry the beams.

I have to mull it over I guess...

doc henderson

some will add sheet plastic as a first layer, with tuffex over the top to protect and develop an air layer to help insulate.  You are suffering the same as me.  want a cheap kiln, but also very efficient.  you will either wind up with time and or money invested.  too many short cuts, and it will not last and or will not work well.  It does not need to pretty as much as air tight, and insulated.  many have discussed adding supplemental heat, but the glazing is the weakest link.  to do that, you need a separated solar panel and container.  now you are talking more money in materials and insulation, with more complexity, fans electricity.  you can do all kinds of foamboard, air dams and valves to stop air flow and insulate at night.  so the greatest thing about this solar kiln, is keeping it simple.  "it is just a solar kiln"!   :D
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

or mill the boards, air dry with fans quickly to 12%, and find a kiln to dry on down, or put in place at 12% accounting for a bit of shrinkage.  I struggled as well.  there is info on a "simple cycle solar kiln"  that is just  a stack of wood and plastic, that might work for your beams.  It also illustrates how containing a bit of heat can speed things up.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

I have dried 2 inch slabs down to 7% using something like this.  Elm out on the driveway.

Simple Solar Cycle Kilns at Timbergreen Farm (timbergreenforestry.com)

I left the bottom open to let water run out, used 16 dollar box fans in the middle of the stack and used a 14 dollar remote temp and humidity monitor.  accurite i think.  
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

etd66ss

I just bought a 40ft container for storage when moving out of my house. For the beams, I place them in the container with a heater and dehumidifier for a couple months? This would be a one time drying event, and I'd do it in the summer/fall before it gets cold as the container is not insulated.

doc henderson

I put my air dried lumber in there, and have a dehumidifier in there.  after the wood is dry I only run it once a month or so.  It has been suggested that you could paint the container black at least on the top and southern exposed walls.  keep it stickered with some cheap fans running.  it is fun to see the bucket daily and how much water literally is coming out of the wood.  I keep a remote temp and humidity probe/monitor in there as well.





 

this is how I bundle logs, and sticker.  the fans go in between and all get covered with plastic, and a plywood cover.  A remote sensor can go into the stack as well.  after airdry, these get moved to the 20 foot container, with fans and a dehumidifier.
 

Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

btulloh

Quote from: etd66ss on June 17, 2021, 05:49:32 AM
Well, I just built up a cart of what I would need for the glazing:


Might have to rethink this solar kiln build. Thought it was going to be cheaper than this...

The whole reason I wanted to build a kiln was to saw and dry ~1000 bd-ft of 1x8 Scots pine to turn into T&G for the ceiling of my house build. As well as 6x10x24ft & 6x6x12ft beams from the same wood. Maybe I'm dreaming that a kiln + me felling the trees and milling the rough boards & timbers would be cheaper. I still need them finished into T&G and re-sawn beams. Though I was thinking I can re-saw the beams and sand them.
Yeah that's the stuff.  When I figured the cost and hassle of doubling the corrugated stuff I ended up with the twinwall.  At the time I was able to get from Home Depot and had it shipped to the store for free.  They don't seem to have 48" wide panels now, just 24", but Lowes has the 48".
I was trying to limit my costs for the kiln just like you and I was able to scrounge a lot of the framing and plywood, but the glazing and insulation costs were the big cost drivers.  Mine was sized to dry 12' lumber, so that's way different from your length.  I also redesigned it a bit so that I could use 8' lengths of the twinwall for my collector.  This of course cut down the collector area and the size of the load, but for me that was an acceptable tradeoff.  I ended up spending about $1600 on the build, which was pretty good and I could have knocked that down a little more if I tried.  Of course your overall length will change that equation.
The one thing I can say is that the value added by building the kiln was such that I would be happier spending more than my original investment even though I only use my lumber for myself.  Having the ability to produce KD lumber easily without any real energy costs gave me much more useful product and really changed my whole dynamic on finished lumber product.
Everyone has their own budgets and requirements to manage, so whether it's worth it for you is another question you'll have to figure out.  Maybe you can get by with a shorter (less expensive) version, or maybe not.  Or maybe it's worth it in the long/short/medium run to proceed with your current size.  Your call.  Anyway, good luck with your kiln project, and especially your ultimate projects.
HM126

scsmith42

Of my 4 solar kilns, three use double pane polycarb panels designed for green houses (greenhousemegastore.com), and one uses a single pane polycarb similar to what you're looking at from the Home Supply store.

I can effectively dry for 2 -3 months more a year with the double pane kilns versus the single pane.  They have the advantage of having closed cell spray foam insulation too though.

About 10 years ago one of our FF members did an analysis of the effectiveness of drying with a double pane glass versus a single pane. It was quite informative in terms of the benefits of the better insulated panel.

https://forestryforum.com/board/index.php?topic=84982.msg1302695#msg1302695

I've had zero issues with moisture in mine.

Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

etd66ss

Quote from: scsmith42 on June 17, 2021, 08:33:46 AM
Of my 4 solar kilns, three use double pane polycarb panels designed for green houses (greenhousemegastore.com), and one uses a single pane polycarb similar to what you're looking at from the Home Supply store.

I can effectively dry for 2 -3 months more a year with the double pane kilns versus the single pane.  They have the advantage of having closed cell spray foam insulation too though.

About 10 years ago one of our FF members did an analysis of the effectiveness of drying with a double pane glass versus a single pane. It was quite informative in terms of the benefits of the better insulated panel.

https://forestryforum.com/board/index.php?topic=84982.msg1302695#msg1302695

I've had zero issues with moisture in mine.
Did you use the 6mm twinwall polycarbonate or thicker?
I think I would have condensation issues being up in the northeast right near the Great Lakes.

btulloh

Quote from: scsmith42 on June 17, 2021, 08:33:46 AM
Of my 4 solar kilns, three use double pane polycarb panels designed for green houses (greenhousemegastore.com), and one uses a single pane polycarb similar to what you're looking at from the Home Supply store.

I can effectively dry for 2 -3 months more a year with the double pane kilns versus the single pane.  They have the advantage of having closed cell spray foam insulation too though.

About 10 years ago one of our FF members did an analysis of the effectiveness of drying with a double pane glass versus a single pane. It was quite informative in terms of the benefits of the better insulated panel.

https://forestryforum.com/board/index.php?topic=84982.msg1302695#msg1302695

I've had zero issues with moisture in mine.
That might have been @YellowHammer that did the analysis. I know he went back and added a second layer to his first kiln. And he's in Alabama, home of copious sunshine and Auburn University.
HM126

etd66ss

Here is something a bit more reasonable, 8 X 16:



 

 

 

Lot less money for the glazing, and the doors aren't crazy.

btulloh

There ya go. Your second one can be the long one. I did an overhang like that on mine. With that overhang you can use a ridge cap to cover the top edge of the glazing which helps keep the length down. A little weather protection it provides on the front helps in my opinion. 
HM126

etd66ss

One question I have is, my design is exactly 16ft long, framing. The glazing panels come in 4ft widths, so 4 panels will be as wide as the framing. Once the siding is added it will protrude out from the glazing on the ends. Should I use drip edge and place it under the glazing so it flares out past the siding?

Basically, should the glazing overhang on the sides?  I'd prefer to do something else there than loose collection area.

Tuftex recommends that the top of the rafters and cross braces are painted white for their corrugated panels, do the same for the extruded twinwall material?

btulloh

As long as you deal with the water somehow (like the drip edge) you should be ok. Just like any roof, details are important and there's always more than one way to get the desired result. 

I painted all my rafters and blocking black on top and no issues. 

There is a thermal expansion factor on those twinwall panels, but they cover that in the installation docs. The joint strips allow for lateral movement and the special self-drilling fasteners  they sell cut their own clearance hole. I just followed the instructions and have no problems. 

They make a sealing strip for the bottom edge that has some drainage holes for condensation. I used aluminum tape and punched a hole every six inches. I'd use their strips next time, because the aluminum tape doesn't hold upin the sun and weather. 
HM126

doc henderson

I think the black vs white color, has to do with heat absorption (obviously).  if the tri-wall is up against a black 2 x 4 it really cannot heat the air, and will poss. heat up the plastic as the wood is slower to transmit heat.  you could use metal for the cross bracing under the glaze, or could angle the edge to support the plastic but minimize the area under the glaze contacting the brace.
your drip edge could overhang a trim piece to keep the water off the exterior walls.  sounds like you will have a nice build.  each additional upgrade makes a percent of improved efficiency.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

farmfromkansas

If you are building a really long kiln, you can stack boards for the header across the opening.  I have built headers by starting with a 2x12, then putting another 2x12 on top of the first one, then rip a piece of plywood to put in the center of the header, and then add another pair of 2x12's to the other side, using construction adhesive between the ply and the lumber, and then nail or screw the whole header together.  Used to use that type header before we could buy these laminated beams. 
Most everything I enjoy doing turns out to be work

YellowHammer

Double panels or glazing is a huge increase in efficiency.  

Don't overthink a solar kiln, it's essentially a black minivan stuck in a mall parking lot in the summer.  It's going to get hot.  However, the hotter it gets, the more moist air you can vent so it can dry wood faster.  

It's not going to do much of anything when there isn't any sun, so during cold dreary winters just becomes a lumber storage shed unless you put a dehumidifier inside.

Paint everything black, including the exterior, to have the entire building become a solar collector.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

Larry

A couple of pictures of my kiln.  It opened like a clam shell.



For the second inside layer of glazing I used 6 mill plastic sheeting.  It worked just fine.  The problem was it only lasted for maybe two years than had to be replaced because it got brittle and ripped.  In the picture it looks like the plastic was near the end of its life.  I used the 6 mill because I was cheap.  As good as the thing worked, I should have used something that lasted because it was a pita to replace the plastic.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

scsmith42

Quote from: etd66ss on June 17, 2021, 08:46:12 AM
Quote from: scsmith42 on June 17, 2021, 08:33:46 AM
Of my 4 solar kilns, three use double pane polycarb panels designed for green houses (greenhousemegastore.com), and one uses a single pane polycarb similar to what you're looking at from the Home Supply store.

I can effectively dry for 2 -3 months more a year with the double pane kilns versus the single pane.  They have the advantage of having closed cell spray foam insulation too though.

About 10 years ago one of our FF members did an analysis of the effectiveness of drying with a double pane glass versus a single pane. It was quite informative in terms of the benefits of the better insulated panel.

https://forestryforum.com/board/index.php?topic=84982.msg1302695#msg1302695

I've had zero issues with moisture in mine.
Did you use the 6mm twinwall polycarbonate or thicker?
I think I would have condensation issues being up in the northeast right near the Great Lakes.
I used 8mm. The ends of the panels are not exposed to the inside of the kiln, and have air exposure at top and bottom.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

scsmith42

Quote from: btulloh on June 17, 2021, 08:50:06 AM
Quote from: scsmith42 on June 17, 2021, 08:33:46 AM
Of my 4 solar kilns, three use double pane polycarb panels designed for green houses (greenhousemegastore.com), and one uses a single pane polycarb similar to what you're looking at from the Home Supply store.

I can effectively dry for 2 -3 months more a year with the double pane kilns versus the single pane.  They have the advantage of having closed cell spray foam insulation too though.

About 10 years ago one of our FF members did an analysis of the effectiveness of drying with a double pane glass versus a single pane. It was quite informative in terms of the benefits of the better insulated panel.

https://forestryforum.com/board/index.php?topic=84982.msg1302695#msg1302695

I've had zero issues with moisture in mine.
That might have been @YellowHammer that did the analysis. I know he went back and added a second layer to his first kiln. And he's in Alabama, home of copious sunshine and Auburn University.
It was a local engineer named Matt. He and Robert think along similar lines though.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

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