Rainscreen Systems
A rainscreen façade is a cladding applied either during
primary construction or as an over cladding to an
existing structure. Rainscreen cladding consists of an
outer weather-resistant decorative skin fixed to an
underlying structure by means of a supporting grid,
which maintains a ventilated and drained cavity
between the façade and the structure.
Euroclad Façades uses a range of metal and metal composite materials (MCM) to manufacture rainscreen cladding systems. MCMs consist of two thin skins of aluminum or other metals such as copper, zinc and stainless steel continuously bonded under tension to either side of a thermoplastic or mineral core.
Rainscreen façades are not normally sealed and
a ventilation cavity of at least 25mm is allowed
immediately behind the cladding panel. Insulation
can be positioned within the cavity and openings at
the top and bottom of clad areas allow for evaporation
of moisture vapour and ventilation/drainage.
A ventilated rainscreen incorporating insulation will
allow the building fabric to breathe without the risk
of interstitial condensation or structural decay.
External wall insulation used in this way is superior
in performance as it eliminates the condensation risks associated with internal or cavity wall insulation.
This is particularly important for refurbishment
schemes. In new construction the use of back
ventilated rainscreen cladding provides the designer
with the opportunity to use economical single skin
load bearing blockwork for infill walls.
The need for complicated damp proof membrane detailing is eliminated and there will be less risk of cold bridging. The air gap provides ventilation and depending on the design of the rainscreen, in conjunction with ventilated panel joints, it may also assist in providing pressure equalisation across the outer skin.
Fully pressurised and compartmentalised (zoned)
systems control airflow locally and are usually used
on high performance, multi-storey developments.
Where lower performance is required, for example
in low rise structures, then a similar cassette panel
system, although not fully pressure equalised,
performs well.
The pressure equalisation concept is simple:
When outside air pressure is transferred to an air
space behind the exterior cladding, the air gap ompartments must be small enough, the air barrier
system must be airtight enough and the area of the
venting through the rainscreen must be large enough
to allow sufficient air to move in and out of the
compartments under the applied air pressure.
The strategy relies on the control of airflow within
and through the wall assembly.
In theory, pressure equalisation means a zero air
pressure differential at all times across the rainscreen,resulting in a complete elimination of the driving force
for pressure-induced water penetration.