I finally decided to go ahead and build a solar kiln. After reading all I could on here and some other sites my dad and a buddy of mine put a plan together a few weeks ago and this morning started working on it. It's going to follow the virginia tech model with a few modifications based on what pineywoods has done. It will be 14'x6'4". My buddy has some old glass windows that he's not going to use. We're going to use those for the roof (is it called glazing?).
I love reading the FF threads that show a project from start to finish so I'm going to try and do that with this. I played around with sketchup a little to get this project planned out. Here's where that's at right now. There are several things we haven't decided yet... mainly what kind of door to do. But the here's the sketchup anyway.
(https://forestryforum.com/gallery/albums/userpics/29264/kiln_sketchup1.jpg)
We have an ideal location for it right on the north edge of a hay field. So if the sun is shining it will be ready to absorb it.
(https://forestryforum.com/gallery/albums/userpics/29264/1-location.JPG)
This morning we cut down an ERC tree and sawed it into two 4x7s on our Woodland Mills HM126. We couldn't get 100% pink heartwood but it's pretty close. And we're going to treat them too. So hopefully they'll last a while.
(https://forestryforum.com/gallery/albums/userpics/29264/2-beams.JPG)
I'll add to this thread as we make progress.
Sounds good. You say,hopefully they'll last a while. We built a greenhouse out of hemlock. When not in use we had the doors open to dry it out. I copied it from a guy that had used white pine for 8 years and it was still standing and looking good.
QuoteAnd we're going to treat them too. So hopefully they'll last a while.
What do you plan to treat them with?
We'll probably treat with a diesel, linseed oil, roofing tar mix. We have some left from another project.
Where are you going to use these two beams? I don't really see the need for treating unless it will be in contact with the ground.
"Beams" was the wrong term maybe. They're going to be skids that the floor joists will sit on. The skids won't be sitting on the ground. They'll be on concrete blocks. Other kilns I looked at used pressure treated lumber for the skids. That's why we're using ERC for them. But since some of it is sapwood I thought it should be treated. I'm totally new to this though. Do you not think the sapwood will rot away if it's left untreated?
With it off the ground and covered by the kiln to keep it dry, not too likely to rot any time soon. However, I don't see any harm in a little insurance by coating it. Don't think you need the BLO in the mix though.
We got the beams cut to length and leveled this morning. We have shims ready if/when it settles.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0802~0.JPG)
Looks good! Your off to a good start. :)
I have a few questions for this great forum:
1. How do you insulate the floor on one of these? The only thing I can think of is to put some sheathing along the bottom of the joists and then insulate between the joists.
2. Should the moisture barrier (I'm thinking to use roofing felt) go on the inside of the studs or the outside? I assume it goes on the inside because that's the warm side and you don't want moisture condensing inside the walls. But I've seen several pictures of kilns with the moisture barrier on the outside of the wall. So I thought I'd double check.
3. Could I insulate with sawdust (from the sawmill)? I realize its R value will be quite a bit lower than fiberglass. But it's free. How much difference would that make in the time it takes to dry a load of sticks?
nrp
Can't tell if the concrete blocks are setting on the ground, or are on concrete pads.
If on the ground, I'd turn them 90° so there is more ground contact than on edge as shown. I think they will have plenty of strength that way and will no as easily sink as time goes by.
And you will want support under each column of stickers as they go up through the stickered lumber.
Put the moisture vapor barrier on the warm side of the insulation (roofing felt isn't a vapor barrier, but is a waterproof barrier).
Dry sawdust should work fairly well as insulation.
Good idea about turning the blocks. We'll do that. They are just sitting on dirt, no pads.
We will have 3x5 joists on 24" centers. The sticker columns will go above those. This is different than the sketchup design above. I hadn't thought it through all the way when I did that design. We're doing 3x5s because we have some left from another project. DonP's beam calculation page says that's strong enough for our 48" span with 125 psf load.
Aaaah, so I should put the roofing felt on the outside and something that actually is a vapor barrier on the inside? Or do I not need the roofing felt at all? What kind of vapor barrier should I look for?
Vapor barrier, 6 mil polyethylene plastic. Placed on warm side. Cover over with 1/2 inch pressure treated plywood.
Does it need to be pressure treated because moisture will condense on it? I'd really like to cut what I need with the sawmill and not have to buy it. If I use ERC planks would that work as well?
Do I need the roofing felt (or something else) on the outside of my studs? Or do I just nail lap siding on and call it good?
You mentioned insulation... if sawdust that will need to be sandwiched in some how. Solid boards or plywood, I'd think.
And in your application (High humidity, etc.) I too would go with treated plywood, although your ERC if heartwood should be a good substitute.
Outside, felt if needing to keep in the sawdust insulation.
I would use the ERC if I had it.
The sawdust will settle over time and need to be topped up a few times. You might also think about treating it with a borate solution for bug prevention and flame retarder. It will need to be dry before placing it in the walls.
Put a full width door or doors across the back side..Build a laminated beam across the rear opening..Your back will thank you when you stack and unstack boards..Especially if you have a fork lift or tractor fel.
I've read that about treating the sawdust with borate. But didn't see many details. Can we use borax? How do we treat it?
Unfortunately we don't have a fork lift or FEL.
Another question: is the facing on regular fiberglass insulation a vapor barrier? I'm wondering if it would really save any money to use sawdust if I need to buy a vapor barrier and borate to use it. Regular insulation may be the same price and less work. Does anyone know if the facing is a moisture barrier?
My brother bought an old house and sawdust was used on the attic floor. I would not want to use sawdust. That stuff has to be dry and you are going to enclose it too.At my brothers house they MIGHT of stired the sawdust around some,since it was in the open.
Regarding the floor insulation, it is best to put a solid layer of wood on the bottom outside of the floor to prevent rodents or insects from entering. Treated plywood is best.
The cost of insulation is small, especially when factored over ten years. Use a closed cell insulation product and not fiberglass. The reason is that if you accidentally get a hole or leak, the fiberglass will quickly lose its insulation vale, will sag, etc. aw dust is not a good idea, as others have mentioned. For a solar heated kiln to work best, you need to keep as much heat as possible inside the chamber, so insulate floor and walls well.
The plywood on the inside should be exterior adhesive, but treatment is not needed as the environment will be quite dry.
Although the vapor barrier is on the warm side, you should also have a vapor barrier in the soil under the kiln to prevent high MCs and the risk of decay or insects. Then, you would have the air space between the soil and the bottom of the kiln.
OK, a layer of wood underneath the joists is what I'll do. I think I'll do ERC boards though (1/2" maybe). It would be too painful to buy wood when I have a sawmill. I'm thinking we'll nail the joists and rim joists together, flip the frame upside down, nail/screw on the ERC boards, flip it back right side up, nail it to the skids, put the insulation in and add the decking. Is that the best way to do it?
I'm too much of a newbie to understand some of the terms. Is closed cell insulation the foam panel type? I looked at those the other day at Lowe's and the thickest I saw was 2". Do I just stack enough of them to get the right overall thickness? Do I need to use closed cell insulation in the walls too or is fiberglass ok there?
Go to the Nyle website, go to Resources, and you will find plans for how to build and insulate a kiln chamber. You can use fiberglass insulation if you cover the inside of the chamber with at least 1" of closed cell foam insulation (Extruded polystyrene) and 1/2" of foil backed insulation (polyisocryanurate). In the chamber that I am building for a Nyle L53 kiln, I am using 9" of R-30 fiberglass insulation between the 2x6 studs, 2" of pink Owens-Corning closed cell insulation over the studs, 1/2" of R-Max foil backed foam panels over that, then a 6 mil polyethylene plastic vapor barrier over the foil backed insulation, then covering the inside with 1/2" treated CDX plywood. Seal the foil backed insulation over all joints and screw/nail holes with silicone caulk and aluminum tape like that used to connect and seal heating and cooling ducts. Then paint the entire inside with fibered aluminum roof coating paint. The chamber has to be water tight.
I would ensure that the seams are very well sealed on the vapor barrier. A vapor barrier that has leaks at the seams works somewhat but the losses that you have will significantly decrease effectiveness.
In theory, you can use fiberglass using the techniques that WDH has given, but because in the real world a wall is never perfectly sealed from the inside moisture, or over time will get a hole in it, moisture from a nail hole, poor construction, mouse, errant piece of lumber, moisture from the wet soil at the bottom of the wall or in a floor, warped plywood, driving rain, heat that makes the vapor barrier brittle and full of cracks, (electrical boxes or plumbing in a house), or some other way, it is best to avoid any insulation that can absorb water. Hence, closed cell, meaning that it will not absorb water, even if the water is present, is best for all insulation. I have seen too many solar kilns with wet insulation to suggest fiberglass.
Most panel insulation products are closed cell, especially the polystyrene or similar types. Some boards are fiber products and do not work well in this application. Dow Styrofoam (R) brand of rigid foam insulation is perfect in this case. Check out a u-tube video...
youtube.com/watch?v=1VpBhY36krg
For the bottom, you could use hardware cloth (wire mesh with 1/4" grid) to hold the insulation and keep out most critters. It might be shepaer and just as effective as plywood.
If you need 4", then use 2 sheets that are 2" each. Around here, the boards are often blue in color.
Incidentally, for a wall or floor, always make sure that you do not seal both inside and outside as this will trap the water. We need the outside to be quite breathable just in case some water does get in the wall.
In a kiln that gets quite hot, some of the foam insulations will melt. So, for a durable installation, use insulation that is not sensitive to temperatures of 150 F or so.
We got some more work done on the kiln this morning.
First we marked where the joists will sit on the skids and set the joists in place.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0811.JPG)
Then we nailed on the double rim joists:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0812.JPG)
Then we flipped it upside down so we could dry fit the boards that will go underneath the joists to hold the insulation in:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0813.JPG)
I really appreciate all the help, especially about insulation and moisture barriers. I think our plan right now is to do the cheapest option (sawdust) but build it to where it would be easy to scoop/vacuum out the sawdust and put in closed cell insulation at some point. So we will build the walls directly on the joists (vs on the floor boards) and use screws for the inside paneling and floor. Based on prices at Lowe's it would cost $450 to insulate with closed cell insulation and $75 with fiberglass. So we want to see how well the free option works first. If it doesn't work well we will upgrade. We don't necessarily need to dry anything super fast. But we do want the temperature to get high enough to kill the wood borers.
Check on price for a do it yourself spray foam kit. Not sure what they cost now, but used to be about $350. Seals and insulates all in one.
Spray foam is typically closed cell too. Good idea.
Lee,
Where was that idea when I needed it ::).
All you had to do was ask me. ;D
I like the spray foam kit idea. We will probably go with that if/when we decide that sawdust won't cut it.
This morning we cut a lot of the studs for the kiln. I didn't take any pictures because studs are boring. But I do have another question about the windows we had planned to use. Here's a picture of one:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0815.JPG)
These are free so I basically sized the kiln around them. I had read in several places that glass was the best type of glazing as long as you don't get hail damage. Then yesterday I read in this thread (https://forestryforum.com/board/index.php/topic,67753.0/nowap.html (https://forestryforum.com/board/index.php/topic,67753.0/nowap.html)) that if the glass has iron it it reduces efficiency. Dr. Wengert said that green edges on the glass means it has iron. My glass is already in a frame so I can't look at the edges. Is there another way to tell if it has iron?
See if you can stick a magnet to it. :D. I really have no idea how to tell if you can't tell that already. ;D
I felt kind of stupid taking a fridge magnet out and holding it to the glass but I did it anyway and it didn't stick. So maybe it's OK. Although a quick google search makes it sound like all glass has iron and and they make some low-iron glass for aquariums and such. I think we'll continue as planned with the glass windows.
This morning we stapled roofing felt to the underside of the joists (with the joist frame flipped up side down).
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0816.JPG)
Then we layed the boards on top of the felt and squared up the frame.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0817.JPG)
Then we screwed the boards down.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0818.JPG)
And then flipped the whole thing back over and centered it over the skids.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0819.JPG)
Next up will be to start framing the walls.
You know I was just pulling your leg about the magnet don't you? I hope you're doing the same back at me. :D
I did figure you weren't being totally serious. 1st grade science taught me that glass isn't attracted to a magnet. But I had to check anyway just to satisfy my own curiosity. I guess there's just not enough iron in there to detect with a fridge magnet.
Don't worry about iron if they were free. The comment is intended for someone going out to buy glass. In truth, the difference is small. If it 10% less! that means maybe three days longer drying.
Made a little more progress this morning. We ripped a bunch of 2 X stuff we had milled a while back into 2x4s for framing. And then cut the angle at the top of the ones for the north and south walls. We decided to cut the angle in the studs instead of doing a birdsmouth in the rafters because of the way the window frames are. They have a lip all the way around and need to fit flush into rectangular frame. So we're doing the top plates at an angle to hold the top and bottom of the window frame. Here's a pic of the window frame lip:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0821.JPG)
The angle will be 36.6*, which we did on the radial arm saw. We went with that angle only because it's close to our latitude and allowed us to use some wood we already had for the floor joists. I hope my trig calculations were right.
Here's our stack of studs:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0820.JPG)
We probably have one more morning on the sawmill and then we'll frame it up.
Really enjoying this thread, as I plan on building my own solar kiln this Spring.
Thanks for keeping us updated.
We've had lots of rain the last two days (over 4 inches on my gauge) so we haven't gotten any further on the kiln. I've been thinking about how to seal around the window frames so rain doesn't get in and I'm not quite sure how to do it. If you look at the sketchup drawing in my first post just picture a window dropping into the rectangle in the roof and being supported on four sides by the lip of the window frame. Originally I was thinking to paint all the wood that holds the window frames and then caulk under and next to the lip of the frame. But I'm wondering if the wood will absorb some moisture and move a little and break the seal made by the caulk. Would it be better to cover the wood with something waterproof? Like flashing or some kind of plastic? I guess I would still put a bead of caulk in between the flashing at the window frames. Or is there another way of doing this that I'm not thinking of?
I would guess that something like silicon rubber which stay flexible would make a good seal.
Butyl rubber caulk is also flexible.
Exciting progress on the kiln.
We put together the the north and south walls.
(https://forestryforum.com/gallery/albums/userpics/29264/photo.JPG)
And put them in place.
(https://forestryforum.com/gallery/albums/userpics/29264/photo_28129.JPG)
Then framed in the west wall.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0822.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0823.JPG)
And then the east wall with the door opening.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0824.JPG)
Next will be the rafters, which I have a question about. We had been thinking to just use 2x4s for the rafters. And we were going to fasten old corrugated roofing panels (painted black) to the underside of them. But I'm wondering if that will restrict the airflow too much. A full stack of wood in the kiln will be 4' tall. If it's all 1" thick boards with 1" stickers then that's 24" inches of height for the air to flow through. The cross section would be 2' by 14' = 28 ft^2. If we use 2x4 rafters that leaves less than 2.5" of height (the windows are sunk in about an inch) for the air to flow through. The cross section would be 2.5/12 x 14 = 2.9 ft^2. Is this a problem? Should I use taller rafters so the airflow isn't restricted so much? How tall?
I'm hoping to use three ~1000 cfm fans in the kiln (still haven't located a third free one). If they're 18" fans then the total area of the holes they will fit in on the plenum will be 5.3 ft^2 (.75^2 x 3.14). If we use 2x6s for the rafters the cross section between the glass and the black roofing panels would be 5.8 ft^2 (5/12 x 14), or slightly larger than the solar collection gap. Should we do that? Or go even bigger? We already milled 2x4s for rafters but we can cut some bigger ones or rig another way to leave more space between the glass roof and the solar collection panels. I'm just not sure how much space we should aim for.
I hope I'm not boring you guys with too many updates.
This morning we got the rafters in. It took more time than I expected because of all the strange angles and joints at both ends of the rafters.
(https://forestryforum.com/gallery/albums/userpics/29264/20131105_150218.jpg)
But we got the three rafters in and the two angled tops of the side walls.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0825.JPG)
My buddy hasn't brought the other three windows over yet so we had to move the one into each spot to set the rafters in place.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0826.JPG)
We're still not sure how much space to have between the glass and the black roofing panels (the question from my last post). If anyone has any thoughts on that please share. We decided to go ahead with 2x4s for the rafters thinking we can string another set of 2x4s between the north and south wall studs to put the black panels on.
Next up (in no particular order) will be:
1. Build the frame for the plenum
2. Paint all the exposed wood on the roof black (we need to let the wood dry out but it won't quit raining).
3. Siding
NRP, I'm a big believer in the black roofing metal on the bottom side of the rafters. Use metal that's about a foot shorter than the rafters, leaving a six inch gap at the top and bottom. You will get a good bit of airflow up the bottom of the metal as well as between the glazing and metal. The real big gain is 50% more collector area and it's perpendicular to the sun's radiation, which makes for maximum efficiency. I like to have visitors open the door and put their hand up against the bottom of the tin, "OUCH, that's HOT" is the usual response. As for loosing available stack height, there's nothing that says you can't narrow the width of the stack as it gets taller. I have done that, no problems....
Thank you pineywoods. I had planned (based on your design) to attach the roofing panels to the bottom of the rafters. But I'm wondering if with the windows I have there will be enough space between the glazing and the panels for the air to flow. With the standard corrugated glazing you get the full 3.5" width of the 2x4, plus a little extra because of the wavy shape of the panels. But my windows are sunk in. So I'll have just under 2.5". That's quite a bit less space. Is it enough?
By the way, I love your engineering analysis and simple easy to build designs. I copied your pineywoods setter and love it. And am now basically copying your kiln. What else have you made that I can copy?
Quote from: nrp0450 on November 05, 2013, 06:36:07 PM
But my windows are sunk in. So I'll have just under 2.5". That's quite a bit less space. Is it enough?
. I copied your pineywoods setter and love it. And am now basically copying your kiln. What else have you made that I can copy?
Can't say about the 2.5 inch space. I'd say try it and see. This whole thing was an experiment to start with. If it don't work satisfactorily, just add a 2X2 on the bottom of the rafters and attach the metal to that..
Now for your last question...home made 4 outlet hydraulics on my kubota M4700, homemade logging winch on the back, homemade forks on the front. Home built hydraulics on what was a completely manual bandmill.. Simmering on the back burner is a home-made band sharpener, but that will be a while, and may not even work..And yes, I do like simple. If it ain't there, it won't break or get out of adjustment. ;D
More progress.
We painted the wood that will be exposed at the roof. We're tentatively planning to stretch a sheet of clear plastic over the whole roof instead of trying to seal it up 100% with caulk. And to have a little higher insulation factor at the roof.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0828.JPG)
We built the supports for the metal roofing panels and the two fans and plenum. We decided to add another set of 2x4s below the rafters to hold the panels instead of fastening them to the underside of the rafters.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0829.JPG)
We didn't put the windows in yet because we're planning to put the roof panels in through the gaps where the windows will be. Here's a pic of one of the panels we're going to use. We're planning to put them in with the ridges running horizontally instead of vertically because it means we don't need as many rafters. It looked like the angle was steep enough that condensation won't pool in the valleys. Is there any other reason to run them vertically?
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0830~0.JPG)
Nrp, you are heading for the same mistake I made. Moisture will NOT condense on the bottom of the sheet metal. It condenses on the bottom of the clear plastic glazing and dribbles down to the bottom, where it rots your front wall. I even built a trough at the bottom of the sheet metal to catch the run-off. Didn't work. Cheap room de-humidifier inside eliminates that problem.. Looks good, keep at it.. 8)
Thanks Pineywoods. I am keeping my eyes open for a dehumidifier. I stopped at a flea market the other day since that's where Planman got his. But they didn't have any.
How does the VT version handle condensation? Or does keeping the vents open at the right times prevent it?
Quote from: nrp0450 on November 13, 2013, 01:01:26 PM
How does the VT version handle condensation? Or does keeping the vents open at the right times prevent it?
Yeah, the idea is to open the top vents to allow the hot humid air to escape, while drawing in cool humid (in the deep south) in through the bottom vents. This effectively limits how dry the lumber will become, and slows the drying. We were told by some knowledgeable "experts" that you cannot dry lumber below 12% in a solar kiln. We dry cypress down to 6% in 4 to 5 weeks.
After lots of rain, some travel, and holidays, we got back to work on the kiln.
We set the corrugated roofing panels up on sawhorses and pressure washed them.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0848.JPG)
Then cut them to the right length.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0849~0.JPG)
Then painted them.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0850~0.JPG)
Then installed them.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0851.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0852.JPG)
Next up will be to cover the walls, install the fans and finish the plenum.
More progress....
We decided to do the exterior of the walls with board and batten. We have quite a bit of pine boards that has some worm holes that we don't have a plan for. So we're going to use it op on the kiln. That meant we needed some horizontal framing to attach the boards to. So we cut a bunch of 14.5" 2x4s and nailed them in between the studs.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0866~0.JPG)
Then we cut the boards for North and South walls and the West wall.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0868.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0867.JPG)
We still need to cut East wall and the battens.
I am liking your build! Very nice progress and pictures. You sound a lot like me with reusing and or the cheaper the better approach.
Mikey
I see 2 things that catch my attention. Why did you leave out the floor boards before framing? And also, having glass windows seems to me will be a problem when a major hail storm hits. I'm NOT being critical...just asking!
If I had glass on the top, I'd probably have a HEAVY tarp handy when a storm was approaching to tie down over the kiln. This would happen probably once or twice a year in Tyler.
The spacing between the covers (the glazing) and the absorber is not real critical. The further away, the better as the heat losses are lessened, so the kiln will be slightly hotter. If the hot collector is close to the covers, heat losses increase, both convection and radiation losses. In fact, that is why many solar kilns use the interior of the kiln as the collector rather than have a separate collector surface.
Glass covers are the best, as they are the clearest and hold heat better. However, if the glass has lots of iron (green color when viewed from the edge) it is not as good. Hail damage risk is why many solar kilns use corrugated fiberglass glazing...not perfect from a solar point of view, but more durable against hail and vandals, and easy to repair.
Two layers of glazing are so much better than just one...they cut convection losses and radiation losses, so there is more energy for evaporation.
Using a corrugated absorber, as you are doing, is a good idea. The more black area that is in the kiln, the cooler the absorber will be (that is, the number of BTUs per square foot of absorber is decreased, so the heating is decreased, even though the total energy input is the same). With more absorber area, the more opportunity for the air inside the kiln to pick up this heat from the absorber and provide hotter air...that is, it is more efficient when transferring the heat from the absorber to the kiln air when there is more surface area.
Based on that comment, would it be more beneficial to put the clear corrugated glazing on the top and bottom of the 'solar' rafters and attached the metal corrugated roofing to the inside walls of the kiln, instead of painting the wood walls black?
Why use corrugated at all? But, yes, the glazing on top and bottom of the rafters is ideal and then put the absorber where you want it.
I was primarily suggesting metal over painted wood, but also noting the increased surface area and mass. Also the big box stores around here don't have large pieces of sheet metal other than the metal roofing.
More progress.... but first an interesting side note. As we were cutting and treating the boards for the siding my mom noticed that the fake wood siding on the little storage building they have has fake worm holes. We were not using these boards for other projects because they have worm holes but the company that built the storage building chose fake wood siding that was designed with fake worm holes. Here are pics of both:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0869.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0872.JPG)
We stapled up tar paper onto the outside of the studs:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0873.JPG)
Then we nailed the boards on. Here are the first few on the south wall.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0874.JPG)
A view of the inside:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0875.JPG)
And some different angles after we got all the boards on:
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0876.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0877.JPG)
We also milled a bunch of 1/2" boards to line the inside with. But I forgot to take any pictures.
Answering planman's questions.
1. We didn't put any floor boards down yet because we're planning to put sawdust in there for insulation. But we want to dry the sawdust (in the kiln) first. Once the kiln is done we're planning to fill the space between the joists with sawdust and let it dry with the first load (or two) of wood. Then we'll seal it in, but leave a way to access it and add more sawdust since it will settle.
2. The glass was free. That's the only reason we're using it. I like the idea of a thick blanket to have some hail protection. If it's easy enough to throw up there we might could get in the habit of putting it on at night and taking it off in the morning and save some of the heat the kiln absorbs during the day.
The real wormy boards look better than the fake ones.
One post said you were considering putting some film over your glazing, check out farmtek.com. Was thinking I saw some reinforced greenhouse film in one of the catalogs.
I think you are creating a MONSTER kiln!! Good work.
After more travel and some distractions (converting a loft to a bedroom for my daughter), we got back to work on the kiln.
We stapled 6 mil film over the inside of the studs.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0908.JPG)
And screwed half inch boards over it.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0909.JPG)
The film we used is the same we were planning to use over the glazing. It was labeled as "clear", but is somewhat opaque as you can see in the first pic. I'm not sure if it will let enough sunlight through to heat the kiln. Does anyone know?
NRP...Really excellent work. Are you keeping track of your expenses? When I build something on the cheap (which is my MO), I like to know at the end of it how much I saved!
No I haven't been keeping track of cost because most of it has been repurposing things we already had. I think the only thing we bought specific for this was the roofing felt.
Almost done with the kiln. I can't wait to get a load of lumber in it. Here's the latest progress:
We finished screwing in the interior wall covering.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0959.JPG)
We pondered long and hard whether to tear out the 6 mil plastic moisture barrier (visqueen) since other solar kiln users here in the south said we would get condensation on it. But we decided that since we were already this far and that we weren't sure how well the sawdust was going to work as insulation anyway, we would leave it. If the visqueen causes problems or the sawdust doesn't work well it won't take too long to remove all the interior pine boards and put in some fiberglass (or blow in) insulation and then put the boards back up.
Then we mounted the fans. Here's a view of the fans from inside the "attic" looking down at them.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0960.JPG)
I don't remember if I said this before. But the fans are free ones from AC condenser units. They seem to move a lot of air and I'm hoping are fairly efficient.
And here's a view looking up at the plenum.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0961.JPG)
You'll notice the gap we left at the top of the walls to dump sawdust in. We're planning to dry the sawdust in the kiln and then scoop it into the walls once it's dry. Then we'll put some styrofoam (also free from the church dumpster) in the gap.
Next we put the glass window panels in and stretched the 6 mil "transparent" plastic over the top.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0981.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0983.JPG)
Like I said before, we were disappointed with the opaqueness but we used it anyway. It still gets quite hot in the kiln. This morning we were working on the tarp that will force the air through the wood stack and up over the black roofing panels. And by 8:30am it was getting too hot to stay in there even though it was 70 outside the kiln (the fans were off and the door was open).
Then I wired in the fans.
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0982.JPG)
(https://forestryforum.com/gallery/albums/userpics/29264/IMG_0984.JPG)
The fans are 240v so I had to find a 240v timer on ebay ($18). I think it's made to fit in an existing enclosure (like for swimming pool pumps and such). Because it didn't have any sort of cover. So we'll have to figure out some way to keep it covered except for when we need to change the on/off times. I also ran a 120v outlet off of one of the poles for the 240v. That way we can plug a dehumidifier in.
We have about half of the tarp left to connect to the underside of the black corrugated roofing panels and then it'll be ready to load.
Expenses to date:
1. 240v timer - $18
2. Door hinges - $6
3. Roofing felt - $16
4. Black paint - $22
5. 6 mil plastic - $50
6. Random fasteners that we already had - maybe $15
7. Cinder block foundation - $12
The wood (framing and paneling), glass, insulation (sawdust for now) and wiring stuff were free.
Total: $139
The kiln is now half full of pine of various sizes (1", 1.5", 3"). I forgot to take a pic but will get one next time.
The other day it was 76 degrees outside and 118 inside the kiln. So 42 degrees hotter. What kind of numbers do others get?