The Industry Foundation Classes (IFC) is a semantically rich data model providing necessary information to support extraction of information necessary for the setup of building energy simulations. Often, 2nd-level space boundary data contained in IFC, are missing or incorrect. To facilitate the connection between BIMs and energy simulation programs, the Common Boundary Intersection Projection (CBIP) algorithm is introduced. CBIP uses the geometric representations of building entities obtained from IFC files to generate the building's 2nd-level space boundary topology. A prototypical implementation of the CBIP algorithm is used in a complex geometry building, as a verification of the capability of the algorithm to properly identify space boundaries.