There are certain portions of the code that can be a bit confusing, or perhaps have been hastily added without the proper review to determine their clarity on intent. Two such code sections are Table 502.2(1) of the IECC, and Table 1015.1 of the IBC.
Table 502.2(1) of the IECC evolved recently from having one easy to read R-Value for walls in most types of construction, to the mysterious appearance of an additional R-Value with a ci subtext notation. Further explanation can be found in Table 502.2(2), which indicates that this ci or continuous insulation means that rigid insulation should be provided on many exterior walls in addition to the normal cavity insulation; however, the logic is never fully explained, even in the commentary. More