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 .

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 with the floor . If that had hit someone , the likelihood is that they would have been seriously injured , if not killed .

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 ‘ homemade ’ rooflights and ensuring that only purpose-made , compliant products are installed .

What makes a rooflight ‘ fitfor-purpose ’?

Here ’ s what to look for when considering rooflights for your next project :

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 .

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 ( eg 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 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 : https :// 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 ‘ non-fragile ’, which is designed to provide a level of safety in the event of an acciden-