Sharp Front analysis of moisture buffering

Moisture buffering describes the use of materials with high water-vapour sorption capacity to provide humidity control in interior spaces. Established models of the moisture dynamics of buffering are derived from conventional Fickian vapour-diffusion equations. We describe an alternative analysis using a Sharp-Front formulation. This yields a similar expression for the  moisture effusivity, several consistent scalings and a new definition of the moisture penetration depth. Features of the model are compared with  some published experimental data. A new sorption buffer index is a measurable experimental property that describes the water-vapour  buffer strength of the material.