Walls
EUREKA!
Archimedes
and the
Cavity Wall
At the junction of a floor and an external cavity wall, the use of lightweight
insulating block and cavity insulation extending below DPC level are now
recognised methods of helping reduce thermal loss around the perimeter
of a building. The Building Regulations require that all such arrangements
prevent dampness from reaching the inner leaf above DPC level that must
remain dry at all times.
The cavity insulation used within a cavity must not absorb water or
promote capillary behaviour. However its presence extending downwardly
around the base of a building reduces the open cavity space available at
the bottom of the external wall - which is where gravitating water ends up.
As the full fill insulation cannot absorb water, one must consider to what
extent accumulating water will be displaced and rise to a greater extent as
a result?
Could it bridge the DPC level? Is the cavity