This paper reviews the problems created by infiltration and exfiltration in buildings, and the design considerations of an air barrier system to control the problems. It explains the air pressures on buildings, the fundamentals of controlling those pressures, air barrier material requirements, combination "air and vapor barriers," and the required properties of air barriers systems. Specific designs will be reviewed, and warm-side air and vapor barriers vs. cold-side air barrier systems compared. The complexities of the "airtight drywall approach," or "ADA," (Lstiburek and Lischkoff, 1986) are also discussed. Finally, the paper will review roof air barrier concepts.

• air barrier