URETHANE FOAM KILN

[fencerowphil (Phil L.)]

I am familiar with two types of hot-sprayed urethane foam products - one being a soft insulation product sometimes sprayed for walk-in cooler insulation or as home insulation, the other being a harder product, used in conjunction with a white elastomeric top coat, as a roof resurfacing product.

Is anyone familiar with using the harder, stronger, roof urethane foam as the insulation and inner wall surface for a solar kiln?
My concept would be to build the outer structure according to one of the many designs in the WoodWeb Knowledge Base, then spray in this inner coat of the urethane. (This is a contractor job, since the equipment is a heated spray rig, using a mixed-at-the-nozzle, two-component, reactive product.) Surface condensation would be minimal, and whatever condensation did occur could not be absorbed by the foam. Paint could be used to protect the urethane from UV, but might not be needed for any other reason.
The floor would be an insulated, reinforced concrete slab/heat sink.
In theory, I believe that such a system, used in south Georgia, with good seals around all vents and access doors, could attain 140+ deg.F. In other words, it could be used at the efficiency level of typical solar kilns, or it could be ratcheted up a notch to do pitch setting in resinous woods or so as to reach lower MC percentages, when required, by more tightly controlling ventilation and cycles. With very little supplemental heat and a double-glazed roof thrown in, 160 deg might be possible in the summer(?)   Bear in mind that only the glazing supports would be exposed to the high heat, due to the continuous coating of foam, so "cooking" your building's frame, etc. would not be an issue.
Has anyone already explored this "in the flesh"?
Phil L.

[Frank_Pender]

Yes, I did.  It was the cost that scared me away.  for a 24' refer trailer the guy wanted $1500 to do just the ceiling and walls.  When I build mine this Spring I am planning on 2 x 6 walls, with the highest rateing I can find, insolated concrete floor, bat and blown in ceiling.  The interior walls, I am planning on lineing with exterior plywood (1/2"), and aluminimum sheeting, with a vapor barrier  between them.  I may look into the foam again just for the fun of it, but the new kiln is going to be 24' deep, 16' wide an a 14' ceiling.  The biggest hinge I have on this whole this is the $  involved. :'(

[fencerowphil (Phil L.)]

Hey there, Frank.
Yes the cost is high.
I hit that wall, when pricing it for a 17000 ft. warehouse I own.
(No, I did not have it sprayed.)

One day, however, I will have some of the six sections of this old building done, and plan to do  a "since you'll be here" deal to ease the pain.

To me, this cost issue is similar to the cost issue in regard to vacuum drying.   You pay big initial bucks for a vacuum job, but increase speed by a factor of, what, ten?  For some operations, I suppose the cost of that is warranted.

Back to our subject, however,....
I am thinking of the investment in these ways:
     Cost of other methods, including labor.
     Potential long-term gains in longevity of the system
       and efficiency of the overall system.
     Flexibility of the resulting system.
     Finally, the fringe benefit of the added structural integrity
         brought in by the hard foam would actually allow one to
         reduce the construction of the shell/frame to a minimum
Phil L.