Teakwood Solar Kiln

[teakwood]

Making progress, first wall is in, it's where the electrical sockets go for the dehumidifier so it needs to be installed first  because all the electrical tubing goes inside the walls

[teakwood]

[Ljohnsaw]

That's one beautiful sauna! ;)

Isn't there supposed to be a vapor barrier on the inside (under the inside boards) to protect your insulation from getting soggy?

[teakwood]

That's one beautiful sauna! ;)

Isn't there supposed to be a vapor barrier on the inside (under the inside boards) to protect your insulation from getting soggy?

I use two layers of insulation because that's what i had laying around. they are 1.5" thick and my wall structure was made with 3x3". I put the first layer with the aluminium side against the inside and the second layer with the aluminium against the outside. kinda of blocking vapor. it's fiber glass insulation so it doesn't get wet, or am i wrong?? do i need to put a vapor barrier on? we don't have that kind of stuff here, can i put normal plastic on?

[teakwood]

another note, the walling is air tight, i hammer the t y g boards together and they are already painted once and we will paint another coat when the kiln is built. do you think lots of vapor will go thru the wood this way?

[customsawyer]

Don't know if you can get it down there and it would be a shame to cover up that beautiful wood but the best thing to paint the inside of a kiln with is what we call Kool Seal around here. It is used to paint and seal older metal roofs. If you use it, put it on thick. I would at least recommend some kind of plastic moisture barrier between the wood and the insulation. 

[YellowHammer]

The kiln should be built like a swimming pool.  Watertight on the inside and porous and breathable to the outside. No moisture vapor should be able to penetrate the inside barrier wall to get to the insulation and lower it's R value, but if it does, it can't stay trapped or it will mold inside the walls and ruin the insulation.  So it must be able to dry from the exterior wall.

Watertight on the inside, porous to the outside.  Plastic, kool seal, Tyvek, spray foam, etc to make the inside layer.  Board and batten, T&G on the outside.  Since kilns use fans to force air through the stacks of wood, they are slightly pressurized and and so force moist air into the walls unless we'll sealed.    

[teakwood]

Thanks guys for the quick answers, i needed to know asap so was able to add a plastic at least to the big backwall.

went to the big city yesterday and found the kool seal paint, another brand but the same specs, was amazed that this siliconized roof paint was widely available here, 37$ a gallon so i bought 3. hasn't much coverage, probably because it's a thick paint.

 

[Walnut Beast]

Looking good!! 

[YellowHammer]

The KoollSeal painted over the wood is very durable and will last forever. I mixed mine with black paint so whatever I painted with it was sealed and black.

The idea is that once the kiln is built, it should last for hundreds of loads with zero maintenance or damage.  I think mine is more than 15 years old and still working.

I also painted mine black on the outside as well.
 

[Klie]

That looks like it is going to work amazing! Great build!

[teakwood]

Here we go, beautiful teakcolor overpainted lol. but at the end it has to work and it's not there for esthetics

Should i do the floor also? i didn't insulate the floor, so it doesn't matter if it gets moist. Planning on putting on 3 layers of paint, is that about right?
 

[doc henderson]

I would say yes on the floor.  It will seal it and help protect the wood.  most of the chemicals in the condensate are from teak wood, but may get really concentrated.

[Walnut Beast]

Some information for you. 
https://vtechworks.lib.vt.edu/bitstream/handle/10919/98866/420-030_pdf.pdf?sequence=1

[doc henderson]

teak what is your latitude?  what is your final angle on the roof?  just wondering.  the primary objective of the vapor barrier and thus the aluminum paint is to seal the chamber and protect the insulation.  if you have no insulation in the floor, then it is not as important from that prospective.

[YellowHammer]

KoolSeal is a reflective thermal barrier, so even without insulation, it would be a good way contain as much heat in the kiln as possible. 

I painted mine flat black, inside and out, floor to ceiling.  The black paint will turn the entire interior and exterior into a solar collector.  During the winter in the sun, my flat black exterior will be noticeably warm to the touch, transferring as much solar energy as possible to the structure.  For me, the solar kiln worked fine when there as a lot of sun, it was when there wasn't sun that I tried to optimize it.  It would be hard to paint the teak on the outside, it sure looks nice.

There is potential that that at some point you may get some standing water on the floor of the kiln, either from washing it, rain, or sometimes there is so much condensation that it puddles on the floor.  If you cut a small 1" drain hole or similar in a convenient place in the floor, and put in a plug, that's one less thing to worry about. 


    

[teakwood]

I will definitively not paint over the wood on the outside :D. Bought a 43 pint dehumidifier, the only "big" unit i could find, for 300$ . we are used to overpay for everything in CR. 

second coat is in and i still have half the paint left. still need to do the doors and the floor

electrical is done with 3 plug ins over the beam. i will put 4 fans in, i thought that more will be better

[teakwood]

teak what is your latitude?  what is your final angle on the roof?  just wondering

we are 11 degrees north. i did 20cm drop per meter of roof, that's about 11 degrees roofangle. you shouldn't go lesser than that, we have heavy rains in the rainseason and they need to flow away. roof angle will not matter alot, our sun here is alot stronger than where you guys live, a dry season day with sun form 6am to 6pm and 100 degrees you want to definitively avoid working in the sun, it's bad. probably need to vent the kiln so it won't melt away :D

[YellowHammer]

$300 isn't bad, and I used one during the winter months to boost drying.  I would take it out in the summer so it wouldn't get cooked and the solar is working full throttle.  

Airflow in a kiln can really help, as long as it's not enough to cause surface checking.  Generally the wetter the wood, the more effect fans have to the point where they can dry almost as fast on wet wood as a kiln, but as the wood dries out, the fans become less effective and that's where the heat from the kiln comes into play.

[teakwood]

not making much progress in the kiln because we had a dry weather window saturday and where able to get logs home, so back to sawing.
 
 
did a diffusor board on the upper edge of the kiln so the airflow increases 
 

[teakwood]

Making progress, dry season is here and i need this oven ASAP.

Mounts for the fans and the collector system


 


the "attic" where the fans should create a vacuum and push the hot air down 





Nice logs, they are getting bigger. This one was 37cm diam, 15"

the color is just awesome, and that's without the water trick

[Sod saw]

.


I chose to paint the floor in our solar kiln white.  

The floor will not see the sun when the chambers are full because the wood casts a shadow and the wood is covered with light weight plywood (painted black) as a baffle and to keep the direct sun off of the top layer of wood.

When the kiln is empty, I did not want a black floor to cause the chambers to overheat without the mass of the drying lumber to soak up that potential excess heat.

I do enjoy working with teak, you are lucky to have an excess amount for your own personal projects.   Although, perhaps it is so common to you as pine is common to many of us; maybe you would enjoy something "different" for a change.


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[YellowHammer]

The best and easiest way to keep the kiln from overheating with an empty chamber is to prop open a door. 

[teakwood]

Man, it's a lot of work to do a proper solar kiln. thinking 2-3 days more and done

[tule peak timber]

Really nice looking! I did a teak job yesterday and was thinking of your operation.