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PRO INSTALLER JUNE 2015
PRO NEWS
@proinstaller1
Intelligent membranes
Interfaces where windows require sealing to the building structure demand innovative, clever solutions in order to
comply with more onerous Building Regulations. The need to eliminate thermal bridging and significantly reduce
uncontrolled air leakage requires robust sealing solutions to meet legislation and ensure long-lasting performance.
The provision of weather and airtight perimeter window seals is
more often than not
achieved with the inclusion of membranes as
secondary seals behind
rainscreens or insulation to built-up walls.
Whilst the traditional
membrane material of
choice is EPDM, this is
being superceded by ‘intelligent’ membranes incorporating variable moisture
vapour permeability. These
can be used to provide either airtightness or weather
tightness. In the latter case,
they act as a breather membrane, preventing ingress of
precipitation whilst allowing
any dampness behind to
escape as moisture vapour.
illbruck’s ME501
The choice of material
is important in terms of
vapour control and when
an inner and outer layer is
involved, it is essential to
consider the relative vapour
permeabilities to allow
moisture to travel from
inside to out. The internal
membrane should therefore
be more vapour tight than
the external. This allows
the building to dry out and
prevents condensation and
mould growth. If EPDM
is used both internally
and externally, interstitial
condensation and mould
growth can result as moisture is unable to escape.
An intelligent membrane
can be used internally
and externally to manage
the vapour control factors
to avoid these problems.
Alternatively, EPDM can be
used as an internal airtight
seal with an intelligent
membrane on the outside;
which still maintains the
‘inside tighter than outside’
principle.
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The membranes used to
seal the windows to the
structure can be connected
to the air barrier membrane
or an external breather
membrane to maintain
continuity of the building
envelope. Fixing to the
window frame can be by
integral self-adhesive strips,
site-applied proprietary
adhesive, or gasket. The
latter provides a mechanical
fix which is not affected by
low application temperatures or damp substrates.
The proprietary solvent-free
hybrid adhesive also offers
an advantage compared with
typical ͽ