HVAC has a bad reputation in the mold-sensitive community—and for good reason. In this module, you’ll learn how to design and install a heating, cooling, and ventilation system that actually supports a healthy home rather than sabotaging it. You’ll discover how thermal bridging, oversized AC units, flex ducting, and poor installation can lead to condensation, mold, and system failure—and how to prevent those problems through better planning and equipment choices. This module covers everything from Manual J/D/S load calculations to ERVs, ducting materials, and maintenance best practices. You’ll explore alternatives like mini-splits, radiant heating, and direct-vent fireplaces, and learn how to design an airtight, well-ventilated, cleanable system that supports great air quality year-round. Whether you're in a hot-humid climate or a dry-mountain zone, this lesson will help you ventilate right and build a system that works with—not against—your healthy home.