Clearview National November 2016 - Issue 180 | Page 58

GLASS&SEALEDUNITS

Insulating Glass
Units standard
and CE labelling
The Glass and Glazing Federation (GGF) has seen
an increase in questions being asked about the ability
of some Insulating Glass Units (IGUs) to meet the
requirements of BS EN 1279-5:2005 + A2:2010.

»»EVALUATION OF CONFORMITY, IN
particular their durability. The IGU design
in question are those IGUs marketed as
Thin, Slim, Heritage or similar names.
These names do not refer to any specific
component brand or tradename, and a more
accurate description of the IGU would be
‘Narrow cavity IGU with reduced edgeseal
sightline’. The main issue in relation to
durability is not about the cavity width, the
industry has successfully produced 6mm
cavity IGUs for many years, but whether
IGUs constructed with an edge seal depth
less than that usually seen in standard IGUs
can be manufactured in accordance with
the harmonised European Standard (hEN)
and be placed on the market in accordance
with the Construction Products Regulation
(CPR), introduced as a legal requirement
for manufacturers in the UK on 1st July
2013.
CLAUSE (24) OF THE CPR STATES;
(24) Except in the cases laid down in
this Regulation, the placing on the market
of a construction product which is covered
by a harmonised standard or for which
a European Technical Assessment has
been issued should be accompanied by a
Declaration of Performance in relation to the
essential characteristics of the construction
product in accordance with the relevant
harmonised technical specifications.
As stated above, with the exception of
IGUs that do not fall within the scope
of EN 1279 series, e.g. vacuum units,
manufacturers of IGUs must, when
placing them on the market, make a

58 » N OV 2016 » CL EARVI E W- UK . C O M

Declaration of Performance (DoP) and CE
mark the product. By making a DoP, the
manufacturer is also confirming that the
IGU is manufactured in conformity with the
product standard.
The issue facing IGU manufacturers
is caused by the growing demand being
generated by their clients, often as the result
of planning requirements, where specifiers
require an IGU with a maximum cavity
width of between 4-8mm, often based on the
planners views relating to ‘double reflection’
and with low overall edge seal sightlines.
This design of IGU is usually driven by the
local authority planning policy that requires
replacement glazing to fit into existing
windows or for replacement windows to
match the existing timber section sizes.
This latter requirement often limits the
glazing platform width and the glazing
rebate upstand dimensions in window
components such as glazing bars or through
astragals. These limitations are of particular
importance when replacing or re-glazing
vertical sliding sash windows (known as sash
and case in Scotland).
IGU manufacturers have responded to this
growing demand by producing IGUs using a
reduced height spacer bar and also reducing
the amount of outer (secondary) sealant below
that recommended by sealant manufacturers.
Once these modifications to the edge seal
are made, manufacturers cannot use their
existing EN 1279-2, EN 1279-3 or EN
1279-4 test evidence to support their claim
of compliance to the product standard when
making a Declaration of Performance and CE
marking these units. At present, the GGF has
not been able to obtain copies of any IGU
manufacturer’s test evidence for these ‘Narrow
cavity IGUs with reduced edgeseal sightline’.

When manufacturing IGUs, it is the
IGU manufacturer’s responsibility to ensure
the products being placed on the market
are manufactured in conformity with the
product standard and have the necessary
test evidence available. If this evidence
is available, it is surprising that IGU
manufacturers producing this type of IGU
are reluctant to provide it.

‘a more accurate
description of the IGU
would be ‘Narrow
cavity IGU with reduced
edgeseal sightline’
The GGF has received a number of
enquiries relating to these units and their
durability. In some instances these units
have shown evidence of failure of the edge
seal construction through condensation
developing in the cavity. This failure may
be attributable to either the durability of
this ‘reduced sightline’ edge seal design or
the method of glazing. Given these units
are used exclusively in timber frames and
are generally glazed using a fully bedded
method, both the IGU design and method(s)
of glazing may be questionable. The cause
of failure may be either of the above or a
combination o