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Dominant Portion
A legacy measurement concept used to determine the boundary of an exterior wall based on the vertical ratio of glass to solid wall. BOMA (Legacy/1996): The boundary is the "Internal Dominant Face." If the glass surface occupies 50% or more of the vertical wall height (from floor to ceiling), the measurement is taken to the glass. If not, it is taken to the solid wall surface. BOMA (Modern 2017/2024): This rule has been abandoned. Modern standards use the "Inside Finished Surface" regardless of glass percentage, which simplifies CAD drafting and reduces disputes over measurement points. IPMS: Uses the "Internal Dominant Face," which is the inside surface of the wall that makes up the largest part of the vertical section. While similar to the old BOMA rule, it is applied more broadly across different building types.