A number of changes were introduced to the SBEM calculation between versions 3.5 (2006) and 4.1 (2010). Further changes have been implemented in version 5.2 (2013). Result differences when running these different versions of the software are to be expected.
Your accreditation scheme provider should always make you aware of changes to calculation methods, however the following information may assist.
"While v4.1.a includes adjustments to a few issues raised through user feedback, the most important modification in this version, compared to v4.0.c, is the upgrade to the calculation methodology for heating and cooling demand within SBEM to the final published version of BS EN ISO 13790:2008 - Energy Performance of Buildings - Calculation of Energy Use for Space Heating and Cooling. The latest version of this standard contains revised methodologies for calculating the heating cooling utilization factors and intermittency adjustments for heating and cooling demands, and SBEM is being modified to align with the ISO standard." (From the BRE website)
For further details on the above please consult the 2013 Part L2A Building regulations and NCM modelling guide.
Please also note that Hevacomp v26 includes additional functionality for accurately modelling room boundaries, which can affect results. For further information please refer to our Partition Centre Lines Wiki.
For A detailed breakdown of the different features of each iSBEM version, please click here