Detailing the 21st-century high-performance building has grown more complicated. Energy-efficiency goals have led to increased continuous insulation thickness, rainscreen claddings, and accommodations for cavity ventilation and drainage. These changes have resulted in deeper wall systems and increased importance on the air and weather barrier and wall flashings as a weatherproofing system. Code requirements for the exterior wall assembly, particularly those outlined in NFPA 285, impact the types of insulation, air barriers, and flashings/closures configurations not requiring custom-tested configurations. These challenges have brought about significant changes to detailing at fenestrations. Meanwhile, the glazing industry has not provided a uniform or standard approach to air barrier transitions to opaque wall systems, given the numerous fenestration types and configurations available. Due to the complicated nature of detailing the myriad of systems and configurations available, designers often denote generic transition details at the critical junction of the wall and fenestration systems. Designs of the fenestration transition are often delayed to the submittal stage when the final system selections are made often after value engineering exercises. If the proposed fenestration system and building exterior design intent are not adequately evaluated, poor performance issues may result in air and water infiltration. Depending upon the complexity of the design, mock-ups are recommended to allow modifications of flashings and seals prior to first installations on the building. The overall relationship of the cladding, insulation, air barrier, flashings, and fenestration must be considered in the design phase because compatibility, functionality, and constructability of the transitions may dictate different fenestration configurations or air barrier transition materials, or both.