Several curtain wall system embodiments are described including dry system embodiments, wet system embodiments and a rain screen system embodiment. The dry system embodiments utilize a subframe grid that is comprised of tubular subframe members. The subframe members are interconnected to form a typically rectangular grid that is attached to the substructure of a building using subframe attachment clips that are longitudinally slidably coupled with the subframe members. Panel assemblies are coupled to the subframe grid in a manner that facilitates a water tight seal. In one embodiment, the panel assemblies include perimeter frame members that can be used interchangeably with dry, wet and rain barrier curtain wall systems.