How moisture moves

Insulation · The Basics · printed page 234 (PDF page 235)

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Moisture – How it Moves Movement of Moisture Insulation – the Basics

Text in the illustration

roof leak
bulk moisture
water wicking up end grain
capillary action
low pressure
high pressure
water molecule
air molecule
vapor diffusion
flow of air and moisture
air-transported moisture

Generated explanation

The illustration uses four panels to show mechanisms of moisture movement in buildings. The bulk-moisture panel shows a roof leak dripping onto horizontal framing below a sloped roof. The capillary-action panel shows water wicking upward through the end grain of a wood member standing in water. The vapor-diffusion panel depicts water molecules moving from the high-pressure side toward the low-pressure side of a dividing layer. The air-transported-moisture panel shows air and moisture flowing through a ceiling opening around a recessed light into the roof space.