The rise in safety checks for solar control glass
Phil Brown, European regulatory marketing manager at Pilkington UK, explains why glass suppliers are fielding a rise in requests from architects for thermal safety checks on solar control glass.
Solar control facades and insulating glass units (IGUs) rise to the call of duty as summer sun finally returns to the UK.
High performance solar control glass is gaining popularity as architects specify more materials that can mitigate against the health risks associated with overheating in buildings, while reducing the need for energy intensive cooling systems with clients’ net-zero emissions targets in mind.
But changing glass trends and risk averseness is encouraging additional diligence with these specifications.
And in recent months, we’ve seen an increase in the number of customers requesting thermal safety checks for solar control glass on behalf of their clients.
The aim of the checks is to reduce the risk of glass breakages post-installation from thermal overstressing.
Glass in buildings can be subjected to thermal stress, which is caused and intensified by temperature differences across the glass pane, and by the distribution of the temperature across its surface.
The more heat a glass absorbs, the more at risk it is. The inherent role of a solar control glass makes it more susceptible to thermal stress, as it absorbs more heat in comparison to other, less absorbing, products.
But what contributes to temperature differentials across a glass pane?
Glass is commonly installed by retaining the edges with a gasket or glazing bead. The area of glass exposed to solar radiation absorbs heat and expands.
The edges of the glass, which are shielded from solar radiation by the frame, remain cooler than the exposed area. The resulting differential expansion causes tensile stress at the edge of the glass. If this exceeds the breakage strength of the glass a thermal fracture will occur.
Of course, if a breakage does occur after installation, then it carries a serious health and safety risk to a building’s occupants or passers-by. There may also be a costly replacement bill footed at the client’s door, which may be exacerbated if the exiting glass is difficult to access
The phenomenon of thermal stress isn’t anything new, yet there’s no clear driving force behind this rise in safety checks.
It may in part be down to the shift away from monolithic toughened glass on the outside of buildings in favour of a laminated glass for its post-breakage behaviour.
A toughened glass outer pane would be thermally safe when exposed to solar radiation, but a laminated annealed glass would be at greater risk of thermal facture, triggering a thermal safety check.
On top of this, an increasingly belt-and-braces approach to facade and cladding safety following the Hackitt Review may also be encouraging more to carry out checks prior to installation.
Most glass manufacturers offer an assessment service for predicting the thermal safety of glazed installations subjected to solar radiation, usually on the completion of a checklist.
Some manufacturers also make the calculation programmes available to customers. For example, the Pilkington thermal stress calculator is available to customers signed up to online resource MyPilkington.
While there may be several reasons behind the rise in thermal safety checks, it’s certainly a sign of architects’ and developers’ increasing commitment to safety in the built environment.
And we’ll be ready to support customers’ safety requirements as solar control glass specifications continue to build momentum in the UK.