In traditional mass walls, e.g. a wall of solid masonry or
earth, the resistance to rain penetration was only one aspect of
enclosure performance (Photograph 1). Heat flow was also
controlled by the thermal storage capacity of the massive walls,
not just by virtue of the materials' thermal conductivity like
the specialized insulation layers commonly used in modern
building assemblies. The sun's heat was absorbed, stored, and
slowly released to the interior and exterior, effectively
damping typical daily fluctuations and thus increasing comfort.
Vapor and airflow were also controlled by the mass of the wall.
It is little wonder that such walls were used for thousands of
years. Built of only brick and mortar, the wall carried all
structural loads as well as performing as an acceptable
enclosure. The small unit size of the brick allowed for planning
flexibility so that such walls could be used for most purposes.
Because mass brick walls allow a considerable amount of heat to
pass through, the exterior surface te