Air, Thermal, Vapor & Water Control Layers in Wall Assembly

On the Mastering Building Science discussion board…
Allison A. Bailes III, Ph.D. answers student questions about air, thermal, vapor and water control layers in wall assembly.

Student 1: 
I’m going to repeat what’s been said about the control layers in my own words, and ask a few questions for clarity:

There’s rain control, air control, vapor control, and thermal control. […]

The Layers and Pathways of Heat Flow in Buildings

In this article, you will learn…

How heat flows layer-by-layer through a building assembly made of multiple materials
Series and Parallel pathways and the varying ease of heat flow between two different pathways, like the framing of a wall or an insulated cavity
Calculations for average U-Values and R-Values

We used to build houses without giving much thought to heat flow through […]