If the Owner asked the contractor (or agreed to his request) to have a BIM model built in order to coordinate the work of the subs, this effort has a cost/ When the underlying systems are changes (e.g. the Mechanical Engineer adds a large ductwork), the 3D model has to be adjusted. This adjustment has a cost as well, and it seems to me that it would be fair that it is part of the Change Order, just as is the time of the superintendent or project manager for the GC/CM. How large that cost should be is a different story. You should perhaps start by getting a breakdown of the hours the BIM team took to modify the model, and what rates they used, and compare them with what your Mechanical Engineer spent in making the original change to begin with. Bear in mind that the contractor's model is usually at a higher degree of precision (i.e. LOD) that the one created by the Engineer.
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Gustavo Lima AIA
Gustavo A. Lima Architecture, PC
Williamsville NY
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