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The Stucco Rainscreen Panel™ System
This system is the most effective method of managing moisture in exterior
wall assemblies is the incorporation of a rain screen. By doing
so, water entering the wall assembly from the exterior, or reaching
the cavity from the interior, is diverted out through weep holes
or dried out by the circulating air through venting.
Water from the exterior can enter any cladding column shortening from
cracks caused by deflection of the main structural elements,
thermal deformation, movements that occur between dissimilar
materials etc. Moisture can also enter the assembly through penetrations
in the air vapour barrier assembly or accidental damage to the
air vapour barrier during occupancy. When this moisture reaches
the dew point it will condensate.
In both cases the assembly must discharge the water to the environment
if the wall assembly is to maintain its integrity and continue
to be utilized in the function for which it was designed. Failure
to dry the wall assembly will cause deterioration to the structure
and may also cause related problems such as; mold, increased
maintenance costs and damage to the appearance of the structure.
If water and moisture remain in the wall assembly, the life expectancy
of the structure will be drastically reduced.
Until now, the most effective way to provide for moisture management
in exterior walls was the masonry veneer or cavity wall. No such
system existed for stucco applications, or rubble masonry.
The introduction of the Stucco RainScreen Panel™ System makes
it possible to construct a true rain screen wall assembly utilizing
a stucco finish system made with cementitious, modified polymer
or acrylic stucco.
 The design of the Stucco RainScreen Panel™ System prevents
any water that penetrates the cladding system from bridging the
air space of the wall assembly by incorporating a cavity. Horizontal
and vertical voids are incorporated into the panel to ensure
that there are effective water and moisture drainage channels
throughout the compartmentalized wall. By design, the vertical
channels of the panel force the diversion of water downwards,
therefore preventing it from penetrating into the assembly and
causing damage. The shape of the upward sloping nodes of the
panel are designed to prevent water from traveling across to
the inner area of the wall assembly forcing the water downwards
towards the base flashing which then expels it to the atmosphere
through the weep holes.
The contact area is of the order of 40% of the panel and its thermal
efficiency is of the order of 60% of that of a solid panel of
equal thickness.
Figure 1 shows the rain screen panel developed by Korax Technologies.
The main feature of the panel is the shape and direction of part
of the panel which comes into contact with the assembly behind
it.
Although it can be made using a variety of materials the use of Type 1
insulation is the most cost effective at this time. The overall
thickness is 38mm of which 26mm is solid and the remaining 12mm
forms the cavity and the sloping basses.
The panel can be used in conjunction with a variety of existing systems
such as cementitious stucco applications, EIFS systems, rubble
masonry walls, metal siding, basement walls, roofs, vinyl siding,
etc. Figures 1 to 5 are typical details for such applications.
The details for using this system are exactly as the details
used in masonry veneer and masonry cavity wall construction.
Any residual moisture that may remain in the cavity will evaporate
as air enters the assembly through the weep holes and circulates
through the vents. This performance makes the Stucco RainScreen
Panel™ System a true rain screen assembly because the water
is effectively screened out of the wall assembly and therefore
prevents moisture and water damage from occurring.
Because the Stucco RainScreen Panel™ System does not allow water
to cross the cavity, and because there are no mortar dropping
into the cavity it can be argued that it will behave better than
a masonry veneer.
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