GLASS & GLAZING
May 2019 • BuildingProducts.co.uk 23
Below: AluK window
in the new-build
Cardiff and right:
at the Pitville
student village in
fully reversible, or bottom-hung for smoke purging.
Open-in windows will impact on internal finishes such
as blinds, so the client will need to be made aware.
Similarly, open-out windows will require a practical
cleaning strategy – either from the ground or in highrise
buildings, via a cradle or abseil.
• Size – Every aluminium system will have a maximum
sash size and, in most cases, the wider the window, the
greater the likelihood that a coupling piece will need
to be inserted to maintain the structural integrity. This
though can interrupt the rhythm and symmetry of the
sightlines, so consideration needs to be given to this
early on in the design process and allowances made if
• Aesthetics – The majority of aluminium window
systems can accommodate almost any design criteria
– from arched and raked heads to dummy sashes so
there’s no need to set limits on what can be achieved.
• Colour – One of the big attractions of aluminium windows
is that they can be specified in any RAL colour or special
finish, including textured, metallic and anodic PPC options.
There are some considerations to bear in mind however
when choosing both the colour and the paint specification.
It is certainly worth taking into account the Light
Reflectance Value (LRV) of the painted surface and the
amount of visible light that will be reflected or absorbed,
in order to gauge how light or dark it will appear
once installed. This is particularly important
when deciding whether to use the same
colour inside and out or whether to
choose a dual colour option.
windows can be
specified in any
RAL colour or
In terms of the paint itself, it should be
a polyester powder paint for aluminium
applied by a Qualicoat approved
applicator to a minimum thickness of
40 microns (60 microns in a marine
environment). It should be specified as
a chromate free preparation treatment or
ideally, with a flash anodised preparation applied
a maximum of 30 minutes before
the powder coating to optimise the
quality and durability of the finish.
• Drainage – Windows need to be
able to drain correctly to prevent
the build-up of moisture or rain
water. It sounds obvious, but it
means they should always be fitted
vertically, unless the systems house has specifically
• Ventilation – Trickle vents are ideal for meeting the
requirement for background ventilation to be placed
1.7m above floor level but the head frame width needs
to be correct in the specification to allow these to
be fitted correctly. Other options include actuated,
electronic opening vents or full-height opening vents
with integral external louvres to provide suitable
background and purge ventilation. System houses and
ventilation specialists can provide advice on the most
appropriate solution to meet the relevant air change
requirements on a project.
• Hardware – This is about safety, security and
accessibility as well as aesthetics. Part M and the
Lifetime Homes standard dictate that window handles
should be accessible for all, which in some installations
will dictate their design and positioning. Similarly,
Part K requires the fitting of restrictors in certain
circumstances to protect from the danger of falling,
and Approved Document Q governs security in new
builds and specifies the fitting of PAS24 accredited
hardware. All of these can potentially take precedence
over design considerations but need not be at the
expense of it.
When it comes to installation, the crucial factor is
getting the correct interface detailing to ensure
that the windows are weather and airtight.
EPDM carriers are generally preferred as
a clip-in to the outer frame. The correct
compound and adequate detailing for
the EPDM needs to be included on the
specification to ensure optimum bonding
with the building fabric, along with the
correct fixing depending on what type of
structure it is being housed in.