The preparation of closed-cell foam insulation test specimens can affect the results of a number of hygrothermal property measurements. In particular, the thickness of the destroyed surface layer affects the measurement of gas diffusion coefficients and thermal conductivity. Multiple specimen preparation methods are in use, as well as multiple methods to measure the thickness of the destroyed surface layer. A ruggedness test, including an interlaboratory comparison, was conducted by an ASTM technical committee to examine the variations due to both of these factors. The results are important in understanding the likely range in values for each preparation technique. The results also demonstrate a sensitivity to the measurement technique.