Back to Basics: Vapor Control Layers Explained | UnBuild It Podcast #163

Vapor is one of the most misunderstood parts of building science—and in many assemblies, it helps buildings dry rather than making them wet. In Part 3 of the Back to Basics series, Steve, Jake, and Pete break down vapor control, vapor permeability, drying potential, and why decades of confusing code language created so much fear around vapor.As Steve puts it, “Vapor is not a liability, it is an asset.” Buildings get wet. In most climates and assemblies, the ability to dry through vapor diffusion is an important part of keeping moisture-sensitive materials safe.The crew explains why you need to understand the vapor permeability of every layer in an assembly, where to find reliable material data, and when to go directly to manufacturers for standardized test results. They also get into indoor humidity measurement and why accurate hygrometers are more important—and more expensive—than many people realize.This is Part 3 of the four-part Back to Basics series covering Water, Air, Vapor, and Thermal control.Pete’s Resources:Water in Buildings: An Architect’s Guide to Moisture and MoldVapor Profiles Help Predict Whether a Wall Can DryICC R702.7 – Vapor RetardersBSC Building Materials Property TableMeasuring and Understanding HumidityASTM E96: Explaining Water Vapor Transmission Rate TestingBuilding Science Advisor