You need to know what the contractor is really doing when they ask about a “crawl space encapsulation”. Sometimes they just go in and add a vapor barrier and leave the foundation vents alone other times the want to seal off the vents. If they are permanently closing the foundation vents they create an Unvented crawl space and R408.3 apply. If they remove the floor insulation N1102.2.11 would also apply. In my opinion if they make a change from vented to unvented a permit would be required.
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