Cavity Walls construction is a modification of cavity walls that were
developed to prevent rain penetration through the masonry by providing a
drainage cavity in the wall. The cavity was an ideal place for the insulation
but filling the cavity with insulation diminished its value as a drain for
Cavity Walls design calls for insulating the exterior faces of the inner wythe
to provide for the structural and insulation components of the wall system.
This wall should also meet the requirements for an air barrier in the
construction. A clear ventilated space is maintained to the outer wythe
which has a number of vent holes to assure there is no wind pressure
differential across the wythe to aid penetration of rain. The exterior
wythe provides the exterior finish for the building. Canadian Building
Digests 40, 44 and 50 by the Division of Building Research (now the
Institute for Research in Construction) at the National Research Council
provide design information for this construction.
PlastiSpan® and DuroFoam® insulation is recommended for Cavity Walls
It is rigid to allow placement to provide a full covering of the wall
surface. It resists penetration of moisture and air and by sealing the
joints the wall can be effectively sealed both to moisture and air
movement. The Cavity Walls design can be effective because it provides
for a complete covering of insulation on the wall.