September 2022

Article Rooflights
GETTING ROOFLIGHTS RIGHT
Total Installer hears from the National Association of Rooflight Manufacturers (NARM),
who discuss the issue of unfit for purpose rooflight installations and provide top tips for
NARM, the National Association of Rooflight
Manufacturers’ purpose is to promote best
practice in all aspects of rooflight design,
specification, installation and maintenance.
As such, we often receive reports from concerned
homeowners, highlighting problems with what they
believed to be professionally installed rooflights, but
which have subsequently been revealed as unfit for
purpose and in many cases, downright dangerous.
making sure installers get it right first time...
With the growing popularity of rooflights and roof
windows among homeowners seeking bright, airy
interiors, instances like these are increasing. One
practice in particular has come to our attention, raising
deep concerns:
A standard double glazed unit installed
horizontally is NOT a rooflight
A rooflight is just like an ordinary window, but installed
into a roof, right? Wrong. Rooflights are subject to
different conditions, different regulations and require
a specialist design approach to provide appropriate
levels of performance, safety and security.
Rooflights should always be supplied to site as
complete units or assemblies, by a reputable
specialist rooflight manufacturer and installed by a
qualified person, to the manufacturer’s guidelines.
Never consider fabricating a rooflight on-site using a
double-glazed sealed glass unit (DGU).
We have seen several instances recently where a DGU
has just been bonded to a timber upstand leading to
a significant safety risk when a pane has failed. In
one instance the unit was ‘stepped edge’ with only the
outer pane being supported by the upstand. The seal
of the DGU was not structural, yet the inner pane was
hanging from it without any other means of support
and probably not a silicone seal, causing it to break
down due to UV exposure. The seal between the two
panes failed allowing the inner pane to just drop from
the roof into the room below. It only broke on impact
Examples of what can happen when a
DGU is just bonded to a timber frame
with the floor. If that had hit someone, the likelihood
is that they would have been seriously injured, if not
killed.
“A rooflight is just like an ordinary window, but
installed into a roof, right? Wrong”
In another recent case, both panes were sitting above
the upstand. Only the inner pane was bonded to the
upstand – and that shattered. It was a toughened
glass pane, not laminated, as strongly recommended
by NARM for this very reason. After the inner pane
shattered, the outer pane could have just lifted away
from the inner pane in the event of a strong wind. An
additional danger was the issue of the glass fragments
falling into the building below.
Also, even without any wind to lift the outer pane, the
building is no longer secure as the outer pane could
just be lifted off the opening. On this installation, there
were exposed metal screw heads immediately under
the glass. It was likely that contact with these metal
screw heads caused the inner pane to shatter in the
first place. It’s also worth noting that the upstand was
well inside the recommended minimum thickness of
100mm to achieve a 0.35 U-value, so this installation
was not only unsafe, but also thermally inefficient.
These and countless other similar incidents serve to
underline the critical importance of understanding the
safety and performance implications of ‘home-made’
rooflights and ensuring that only purpose-made,
compliant products are installed.
What makes a rooflight ‘fit-for-purpose’ ?
Here’s what to look for when considering
rooflights for your next project:
Safety
Current British Standards define that inner panes
on rooflights must be laminated in applications
more than 5 metres above floor level (increased
to 13 metres in limited circumstances) or are
located over water (e.g. swimming pools).
However, the relevant standard permits use of
toughened glass inner panes in other applications,
if a risk assessment is carried out and confirmation
provided that this does not present additional risk to
66 T I SEPTEMBER 2022 PRACTICAL CONTENT FOR THE GLAZING INSTALLER & HOME IMPROVEMENT SPECIALIST