BIM only takes more time if coordination is a new aspect to consider. Once the expectation of a 3D BIM model becomes a first cost construction savings, the design process must consider integrated systems that are coordinated at a high level of detail.
This is not the normal “standard of care” for Architects and Engineers. Owners are often sold on the idea that if everyone is doing BIM, the schedule will absolutely be accelerated and field orders reduced. The truth is that BIM tools are as segmented by discipline today as any CAD was yesterday. What I mean by that is design teams are not forced to cross-reference each other with the new tools. In fact, when project mangers raise the expectation to do so, it is disruptive to processes that are moving in a traditional semi-silo-ed manor based on a few mid-design spot checks of overlaying schematic systems. Waste from post integrating BIM segments will come in the form of rework. The rework will likely be a result of modeling progression that is out of sequence. If design processes are to meet the expectation of trouble free installation the need a plan to progress through design is a logical sequence to avoid rework.
One of the reasons why design-build IPD contracts work so much better in getting to highly coordinated BIM models is that they lend themselves to planning that would involved AEC, GC, subs and owner at the same planning table.