Condensation in Buildings - Australian Building Codes Board

Information Handbook: Condensation in Buildings
material to achieve all four principal control functions A closed cell, high density foam (32
kg/m³), spray applied to the concrete block leaf, serves to control the movement of water, air,
water vapour and heat across the assembly. The resulting wall can operate successfully in any
of the eight US climate regions (illustrated in Figure 4.5), adjusting only the level of thermal
insulation to suit the location.
The exterior surface of the foam forms a drainage plane to discharge any penetrating water
from the cavity and this cavity must be drained and vented (“Vented”, in this context, means
only that the cavity can respond to changes in atmospheric pressure. It does not necessarily
need to encourage the through flow of air). Since the high density spray foam has a high
resistance to water vapour, the components on each side of that layer are expected to dry away
from it in one direction only.
By contrast, the residential wall in Figure 5.17 relies on being able to dry in both directions.
Figure 5.17 – Insulated stud frame wall with brick veneer cladding
(Source: Lstiburek 2011b, Figure 6)
brick veneer
external cladding
drained and
ventilated cavity
drainage plane
exterior sheathing
Cavity ventilation
HEAT
WATER/AIR
exterior sheathing
steel or timber studs
(insulated)
interior stud space
insulation
(heat control layer)
DRAFT HANDBOOK
plasterboard lining
with latex paint
Australian Building Codes Board Page 71