Facts About Foam Plastics To the Editor: I read with great interest your February article on stressed-skin panels where author Alex Wilson compares isocyanurate (Iso) and expanded polystyrene (EPS) insulations. While I agree with a number of his assertions, I wish to clarify and expand upon some points in his article. First, it is evident that Mr. Wilson has not visited an EPS manufacturing plant, for had he done so he would have seen a much more complex manufacturing operation than he would have your readers believe. Manufacturing EPS blocks and panels is far more complicated than pumping two chemicals from 55 gallon drums, as is generally the case in manufacturing isocyanurate products. Second, Mr. Wilson speaks of lower R-values for EPS (R-4.17 at 40øF and