Insulating kiln

[logbyr]

In process of insulating chamber for my nyle L 200.   I have my  2" foam between studs done and am now starting to put my 2 layers of 1/2 " Celotex.    Do I need to caulk all the seams and nail holes on this or just the layer of plywood that will cover the celotex and 6 mil vapor barrier.   Thx in advance

[GeneWengert-WoodDoc]

Seal the vapor barrier seams very very well.  Repair any tears or nail holes.

One caution is that if you seal the plywood totally (and this would mean that sealing the seams should also be done) and in addition also,use the plastic vapor barrier, any moisture that gets between the two will be trapped and so will make ideal conditions for rot and corrosion.  Use one, not both.

The interior plywood does help with building rigidity and does provide protection from flying pieces of lumber that hit the walls.  People that do not use a plastic vapor barrier do seal the plywood instead to prevent moisture moving into the walls, with the moisture causing deterioration and loss of insulating properties.

The plywood edge does not need sealing, as moisture can move through the faces easily, so the edges are not an issue.  On the other hand, using a roller with a thick coat of asphalt roof cement on the four edges wouldn't hurt, especially with CD-x -plywood.  However, with the openness of plywood edges, it would be impossible to seal the edges.  Note that CD-x uses the same adhesive as higher grades, including marine grade.

[logbyr]

Gene,

Thx for info.   Confusing part for me is u repair all holes in one layer then you add the next layer and drive nails thru original layer to attach it.   

[GeneWengert-WoodDoc]

We hope that the nails go though the plastic and because the hole is held tightly by the wood pieces on each side, and the nail hole is tight to the nail, that little moisture can move through these holes.