The building enclosure is intended to control and moderate how air, water, vapor, and heat communicate between interior and exterior environments of a building. Practitioners need not guess how a building will perform. Good design and construction can be informed by an understanding of the performance characteristics of the building enclosure, and testing can be utilized to verify the functional performance of the building enclosure. The presentation will provide an overview of building enclosure performance, introduce concepts for characterizing building enclosure failures, and present test methods used to verify the performance of the building enclosure. The presentation will include a live demonstration of air and water penetration resistance testing on a standard window with an open discussion of ASTM and AAMA Standards.