Some customers ask about how best to enter foam filled block walls. Some insulation marketers advertise very high RValue for the foam filling. However the core of the block is not where much of the heat transfer occurs. The web of the block is where considerable heat transfer takes place. 

EnergyGauge USA has limited number of wall types. The one that best represents foam filled core products is called "Concrete Block - Polystyrene Bead Aggregate."  As shown on the EGUSA software walls page this approximately reduces the U-Value of an otherwise uninsulated block wall in half (you can try it for yourself).

Does even higher R value cores change a great deal? We used an ASHRAE Handbook of Fundamentals 2009 example and formulas (equation 7 and 15 in Chapter 25). ASHRAE provided an example of perlite filled core (R value of 14.86 core insulation). We compared that to a product that would have a core of R Value of 22.65. It results in a very small increase in R Value of the overall wall from 3.42 to 3.53; rather negligible whe n it comes to energy savings. To improve concrete block walls more, add interior or exterior insulation that covers the entire block.  

If such small discrepancies concern you, consider that some cores are usually filled with solid concrete and rebar for strengthening. This core becomes highly conductive and would reduce the overall wall value factor.

In conclusion, EnergyGauge tech support recommends selecting "Concrete Block - Polystyrene Bead Aggregate" for any concrete block wall with insulated cores.