4 x 8 sheets of plywood, R-10 rigid styrofoam insulation, food grade panels assembled into a giant box. Two internal fans for air movement. Stainless steel racks for shelves (4) and radiant fin, hot water heater strips powered by an overwhelmed residential water heater. Circulating pump, make up water tank, low water cut off, hi temp cut out, TPV and you're all set :-) Good ventilation was a belated addition ;-) -Jim C http://www.StepUpForCharity.org Mild to Wild(R)