Rainscreen Technology

Vancouver, BC is the largest city in the province ofform of rain, by sealing the exterior of the wall and
British Columbia and the third largest city in Canada. Itpreventing water from penetrating past the face of
is surrounded by water on three sides and is nestledthe cladding, if water does penetrate past the
alongside the Coast Mountain Range. In addition to acladding it cannot readily drain out of the wall and
spectacular natural scenery and a bustlingremains, therefore, stagnant within the assembly.
metropolitan core as well as boasting one of theHere water can damage moisture sensitive material
mildest climates in Canada, Vancouver records one ofand components. It is, therefore, essential to insure
the heaviest rainfalls in the world. Typical rainfallthat no water penetrates the outer cladding.
monthly patterns average 169 mm each in NovemberThe water management strategy created by
and December and 135 mm in February and March. Inface-sealed outer wall assemblies can work in certain
Vancouver anything can happen to you, but dying ofconditions where the wall is in a protected location
thirst is not one such thing. Vancouver, furthermore,and receives little exposure to wetting. However, as
holds one other record - although this one is verywe have so disgracefully learned first-hand here in
seldom publicized on tourism websites: it is the leakyGreater Vancouver, in most situations face-sealed
condo capital of Canada.walls do not perform well. This is so because it is
To be fair to my hometown, Vancouver is not byextremely difficult to fully seal the exterior cladding
any means the only place in the world to haveand ensure that no water will enter. The increased
experienced this kind of problem. Toronto andexposure experienced by high-rise buildings further
Winnipeg have suffered of the same calamity, and solimits performance expectations for this type of wall.
have Chicago and London, England. The problem here,In contrast, rainscreen walls manage water in a
however, is that a lot has been said and very littledifferent fashion. The exterior cladding is still intended
done to correct building envelopes imperfectionsto deflect most of the water that contacts the wall.
common to so many high-rises, until the aggregateHowever, a cavity is provided behind the cladding. If
estimated cost of repairs to leaky condos haswater does penetrate the cladding it reaches the
exceeded CAD $1 billion. Engineering, now, has comecavity and cannot move further into the wall
to the rescue changing things finally for the betterassembly. Instead water in the cavity will drain down
with a new advance in building envelope constructionon the inside face of the cladding or on the
and repairs. It is called Rainscreen Technology.waterproof membrane at the other side of the
Most of the high-rise towers have been built usingcavity, and it will be deflected out of the assembly at
face-sealed outer wall assemblies. Developers refera cross-cavity flashing. In practice the cavity acts as
to 'cladding' as the material or component of the walla capillary break to remove the capability of water to
assembly that forms the outer surface of the wallstagnate inside walls. The end and most important
which is, thus, exposed to the full force of theresult of all this is that with rainscreen walls it is not
environment. Face-sealed outer wall assemblies haveessential that the outer cladding be completely sealed.
invariably relied on a strategy for rain penetrationImperfections are acceptable, and this will surely
control based on the elimination of holes through themake a lot of developers happy - and a great many
cladding. As face-sealed walls are designed andcondo owners even happier.
engineered to deal with exterior moisture, in the