Kiln Container Built from Wood

[DR_Buck]

I've ordered a second Nyle kiln, an L53 so that I can dry the small loads  I have customers bringing.    I will be building the container for this one instead of using an insulated sea container like for my DH-4000.  Many times I have customers with only 300-400 bf for drying.   My thought is to build the box large enough to hold  no more than 1000 bf.    I currently have a large amount of poplar and plan on building the box using that for framing and board & baton outside.   The floor will also be wood, probably untreated white oak.    It will be insulated all sides and top & bottom with 5" thick close-cell foam sheeting (R6 per in).   Then I thought maybe cover the inside walls with horizontal edge to edge 1x boards.    

Questions are:

1 - What will the impact of the changing moisture content do to the inside wall covering if it is 1x boards?

2 - Should I coat them with waterproofing such as aluminum roof paint, something else or leave them bare?

3 - The close cell foam board is water resistant, so I'm assuming I don't need a plastic vapor barrier under the inside       wall boards.     Correct?

Any other suggestions welcome

[Southside]

What is the temperature rating on your foam?

[farmfromkansas]

The closed cell foam will not absorb moisture like bead board, so it is a vapor barrier.  However, if you are using wood framing and putting the foam between, your framing could absorb moisture, so should probably put a layer of film over the wall on the inside.

[DR_Buck]

What is the temperature rating on your foam?

I don't know, but it is high.  It does not melt and it is fire proof.   Used it in my new addition and the building inspector tested it.

[GeneWengert-WoodDoc]

It is a good idea to use a plastic sheet on the inside.  Without it, there will be cracks and crannies that will allow vapor to move into the wall and condense on the wood, creating ideal wood rot conditions, plus moldy odors and even corroded nails and screws.  

When nailing the interior wood pieces, use stainless or aluminum nails, or else the heads can corrode and soon you have board coming off.  CD-x plywood is a much easier material to use and goes up faster, is easy to coat with a vapor barrier coating, but still use plastic underneath, easy to repair, moves less as the interior humidity goes from very humid to dry to humid, etc.

[kelLOGg]

I "painted" the inside of mine with aluminum roofing paint and it has held up very well for more than 12 years. I suited up, wore gas mask and swabbed floor, walls and ceiling and put thin plywood over the floor for foot traffic. I'd do it the same way again if I had to.

[YellowHammer]

The build theory of a kiln is to configuration is just like a swimming pool, with the waterproof liner on the inside and th more permeable materials further to the outside.  So it really wouldn’t matter what the outside was made from, as long as it insulated properly and completely waterproof on the inside.  

I used plywood on the inside, calked the seams, and then laid in a couple coats of the silver roofing sealer.

[scsmith42]

Three of my four solar kilns use closed cell insulation inside.  They are sprayed pretty much even with inside of the wall studs.

The inside is sprayed with an asphalting black roofing paint (except the floor).  No issues in several years.

[woodfire]

there's a home built kiln on my property that was put up back in the 60's or 70's and has only 1/2 plywood sheets for doors and corrugated metal sides and roof, wood drying area built above a 3'-4' crawlspace that has large fans in it. it was used successfully for decades Ive been told. 

[K-Guy]

For the boards only shrinkage is a concern.
A vapor barrier should be used and the walls painted with the aluminized roofing paint.

[farmfromkansas]

I was thinking about the build up of moisture inside the walls of a kiln.  Have seen small devices designed to allow walls to dry out, creating small gaps between boxing and framing.  Maybe just using corrugated metal to finish the outside, and maybe using no sealer for the gaps, creating a small vent top and bottom to allow a little air to dry the wall out on the outside.  Any comments?

[GeneWengert-WoodDoc]

Your idea is ok if we only had vapor to worry about.  However, it is common that the vapor turns to liquid and then it becomes hard to Move out of an enclosed space...kinda like spit inside a balloon.