Abstract: A building includes a coupling apparatus providing an interface between a drywall and an exterior curtain wall mullion. The coupling apparatus includes a first member in contact with a first face of the exterior curtain wall mullion and a second member in contact with a second face of the exterior curtain wall mullion. The first and second members are joined by an elastic or spring element and pivotally coupled to a bracket attached to the drywall. Insulating material may be placed between the first and second members to provide sound insulation. The coupling apparatus permits inward and outward movement of the exterior curtain wall with respect to the drywall during windy conditions and side to side movement of the exterior curtain wall with respect to the drywall during earthquake conditions.