Walls are one of the most important—and most misunderstood—parts of a healthy home. In this module, you’ll learn the recipe for building wall assemblies that are resilient, mold-resistant, and energy-efficient. You'll learn how to practically apply the four control layers: water, air, thermal, and vapor. We’ll explore the “Perfect Wall” concept from Dr. Joseph Lstiburek and how to adapt it for your specific climate and project. You’ll also learn best practices for framing, air-sealing, rainscreens, insulation, and outsulation, as well as how to prevent moldy lumber, moisture intrusion, and hidden condensation. With detailed guidance on everything from insulating window headers to blower door tests, this module equips you with practical strategies to build walls that keep your home dry, airtight, and healthy for the long haul.