Episode 3 of Build Science™ 401 details a crawlspace or “short basement” foundation using real 2D and 3D drawings to show how water, air, vapor, and thermal control layers must align and remain continuous. Matt Risinger and Steve Baczek explain how elements like sub-slab insulation, drainage, closed-cell spray foam, and exposed foundation work together to manage moisture, air leakage, energy performance, durability, and region-specific risks like termites and frost depth. A major theme is continuity—tracing each control layer from below grade up through the wall assembly—and understanding how different insulation types and permeance levels affect drying and risk. They emphasize that these details are not theoretical but taken from an active, under-construction project, reinforcing the importance of learning from real-world, proven assemblies.