Sorry for the confusion. Unless I misread, I think the contention in the article, and in Roger's posted response to questions above, is that sleeping pads *are* rated in SI (including Prolite, speced R-2.2 or 3.8 for Prolite Plus). If the rating *was* imperial, that would seem more in line with building insulation materials.
Assuming pads are SI rated, I wondered if the R rating for pads assumed a greater temperature differential than the R rating for building insulation (converting units, of course). By R= m^s*C/W, that would give a bigger number for R, if cross-sectional area and watts are held constant. I assume there is some standard value for temp. differential and watts so that the R for different insulations can be compared.
My training is in architecture and the building trades--R values are something I've always looked up, and used to calculate heat loss. So my assumptions may be way off base.