September 2022

around the edges.
A reputable rooflight supplier would be able to
provide these accurate values for their product.
Security
Part Q Building Regulations state that ‘Ground
floor, basement and other easily accessible
windows (including easily accessible rooflights)
should be secure windows made to a design that
meets the security standards of British standards
publication PAS 24:2012.’
those below the rooflight.
The term ‘toughened’ implies a degree of safety which
in the case of rooflights, is misleading. Toughened
glass inner panes actually bring a risk of shattering
and falling into the room beneath. Therefore it’s
difficult to see how use of a toughened rather than
laminated glass inner pane doesn’t present a risk
to anyone beneath a rooflight, whatever the position
or height of the installation. For this reason, NARM
asserts that any risk assessment of a toughened inner
pane is largely irrelevant.
For the safety of people needing to access roof areas,
non-fragility classification should also be confirmed.
The Centre for Window and Cladding Technology
(CWCT) has devised specific non-fragility tests for
large area glazing. These are referenced in the latest
issue of ACR’s (Advisory Committee for Roofsafety)
Red Book and NARM has published a document
entitled Understanding CWCT Classifications of
Rooflight Types. This can be downloaded free of
charge at: www.narm.org.uk/new/wp-content/
uploads/2021/08/NARM-Quickguide-8-CWCT-
Classifications-1.jpg.
Another important point to be aware of, is the very
great difference between a rooflight classified as ‘nonfragile’,
which is designed to provide a level of safety
in the event of an accidental fall onto the rooflight;
and a ‘walk-on’ rooflight, designed to allow frequent
foot traffic for a roof terrace, for example. Walk-on
roofllights are designed and built to floor loadings, to
match the surrounding roof area – and are therefore
much heavier and significantly more expensive
than conventional rooflights. For more information,
download our publication: Understanding the
differences between non-fragile rooflights and walk-on
rooflights: www.narm.org.uk/new/wp-content/
uploads/2021/06/NTD11-2017.pdf
Thermal performance
Approved Document L of the Building Regulations
defines the requirements for Conservation of Fuel and
Power by setting the standards for energy performance
and carbon emissions for new and existing buildings.
This part of the Regulations has recently been
updated. In respect of rooflights generally, the limiting
rooflight U-value is now 2.2 W/(m 2 K) when assessed
in the horizontal plane. It’s important to note that the
quoted U-value needs to be for the whole rooflight, not
just glass centre pane U-values, which we still see
quoted by some suppliers.
A cutaway of a rooflight, which should
always be installed by a qualified person
“Even a fully compliant, high quality rooflight can
be compromised by inappropriate installation
methods or standards on site”
Even when just a DGU has been bonded to a timber
upstand, the centre pane U-value is not the U-value
for the installed rooflight as account has to be taken
of the spacer bars and edge seal of the sealed unit,
the centre pane U-value excludes these heat losses
A PAS24 certification is a security standard that can
only be met once a product has been certified for
its security performance. The acceptable security
standard ensures that products meet high-security
performance levels, offering reassurance to
homeowners that the entry points to their homes have
been rigorously tested and are resistant to break-ins
and home invasion.
Products satisfying other standards that provide
similar or better performance are also acceptable.
These standards include: STS 204 Issue
3:2012; LPS 1175 Issue 7:2010 security rating
1; and LPS 2081 Issue 1:2015 security rating
A. Frames should be mechanically fixed to the
structure of the building in accordance with the
manufacturer’s installation instructions.
Other considerations
Even a fully compliant, high quality rooflight can be
compromised by inappropriate installation methods or
standards on site. For this reason, we strongly advise
close adherence to manufacturers’ installation guides
and reference to any specific requirements relating to
roof finishes abutting the rooflight.
A simple way to ensure that the rooflights you
specify for a project will meet appropriate standards
and regulations, is to source them from a NARM
member company. Our membership comprises
businesses supplying all types of rooflights and
NARM membership is only open to businesses whose
products are fully compliant.
Contact NARM:
0161 224 7477
www.narm.org.uk
@_NARMUK
PRACTICAL CONTENT FOR THE GLAZING INSTALLER & HOME IMPROVEMENT SPECIALIST
SEPTEMBER 2022 TI 67