Increased pressure on glass

Centre pane failures in triple-glazed IGUs represent an area of growing industry concern. Dave Broxton, managing director of Bohle, discusses.

At the beginning of this year a meeting of the GGF was held to discuss the proposed revision of Part L, which sits within the government’s wider consultation on Future Homes.

The two options on the table are: one, to make triple-glazing compulsory in new build; and two, to drive improvements in U-values.

The meeting returned a resounding verdict that they would much prefer the second of the two options.

There are obviously multiple factors that had an impacted on that choice: increased costs, increased weight in installation, need, and more.

There is, however, another factor that may have been nagging in the minds of IGU manufacturers: the growing number of failures reported in triple-glazed units. I’m pretty certain that this is not the ‘Triple-glazing question’ that the industry was referring to three or four years ago.

The reality is that the failure under thermal stress of centre panes in triple-glazing could cost the industry £hundreds-of-thousands.

The use of low-e on face three of the unit as part of its thermal make-up can lead the middle pane in a triple-glazed unit to heat up far more than it would do in a standard double-glazed unit. This increases the pressure on the glass.

In larger units this is less of a problem as the glass can flex and the pressure can be absorbed. Within smaller units with shorter edges, the glass is, however, essentially too stiff to bow out and it can lead to stress cracking of the centre pane or failure of edge-seals.

The problem is obvious. The more triple-glazing the industry sells (demand is growing, regardless of your view on the benefits that it delivers over and above double-glazed options), the more it has potential to store up problems for its future.

Bohle is doing its part to support the industry in finding a solution. We’re contributing to a Europe-wide study, which includes specific focus on edge-quality and how the glass is cut as a cause of failure.

Edge-quality is a known cause of failure in glass, units or otherwise. In cutting glass you’re putting tension into it. Get the angle or shape of the cut wrong, or use the wrong cutting fluid, and product is going to be less stable.

It may not be the sole cause of centre-pane failures in IGUs but indicative test results suggest that it plays a part.

This is why the right choice of cutting wheel and fluid in any industrial cutting process is key. Get it right and you’ll manufacture a better product, lose less material in the furnace, and go some way at least to insulate yourself against future claims for failure. This is especially true if you’re manufacturing triple-glazed units.

This is where Bohle can help. Our iconic Silberschnitt cutting wheel range has evolved over almost a century from simple hand-held tools to high-tech automatic cutting wheel designs. We support our customers in selecting the right cutting wheels and the right cutting fluids for an almost limitless range of applications.

We work in partnership with companies including Glaston Bavelloni, Bottero, Bystronic, Benteler, CMS Brembana, Grenzebach, Hegla, Intermac, Macotec and Lisec, to help them optimise performance of industrial glass cutting lines.

We can’t guarantee that we can eliminate the risk of failures in centre-pane IGUs but we can support you in addressing some of the risks.