Construction feature options in CoolCalc are derived directly from ACCA tables. Not all possible constructions are covered in ACCA tables so if you don't see the exact option you are looking for, selecting a substantially similar option is acceptable.
Newer homes may have better R-values than the available selections from ACCA tables. As R-values increase, the energy efficiency benefit between R-values becomes relatively smaller so using the nearest available R-value is acceptable in most scenarios. CoolCalc does not yet implement custom R-values (MJ8 appendixes 12 and 13), if you believe the construction features of the home are substantially different than the available options in CoolCalc, please follow ACCA procedures in MJ8 appendixes 12 and 13.