Air today, not gone tomorrow
Andy Everett, national account manager at Swisspacer UK, says with skyscrapers getting taller and taller, the impact of increased atmospheric pressure on installed glass units is becoming a growing consideration for specifiers and sealed unit manufacturers.
Our history as a country where church steeples and cathedrals were the highest structures is no more. The UK’s landscape is changing dramatically, with property developers keen to squeeze in taller, thinner skyscrapers than ever before. There are currently 142 new skyscrapers either under construction or proposed as of 2019 in the UK, largely concentrated in London.
Whether residential or commercial, huge sections of glass curtain walling and oversized sealed units are being specified. Principal Tower, designed by Foster + Partners, is due to complete this year and will be one of the tallest residential buildings in London, with 6,700m² of glazing used.
The glazing is often manufactured elsewhere, and each extremely heavy section has to be carefully taken to site. Increasingly, sealed unit manufacturers and window and facade fabricators must consider the variation in air pressure between the production site and place of installation. But with skyscrapers getting taller and taller, the difference in air pressure between installed units from the ground level of a building to the top is also crucial. It’s not unusual to notice a bowing effect in units in upper levels due to increased atmospheric pressure.
Swisspacer Air is a small metal sleeve with an integrated membrane that fits unobtrusively into the Swisspacer spacer bar, so is not visible within the unit. It can be installed within extremely large units in commercial or high-rise residential buildings, to help reduce glass deflection and the risk of a failed unit. Designed to regulate air pressure and prevent sealed unit failures by counteracting climatic load, it also reduces the rippling effect on large units for a consistent finish.
When IGUs are exposed to cold temperatures, panes bend inwards and, in extreme heat, they bulge outwards. Air means that pressure equalisation can slowly flow in through the membrane, or overpressure can be slowly released and balanced back out between the panes. It does not require expensive gases such as argon within the pane.
Travelling at altitude is also an important consideration. If glass is being transported between vast altitude differences, such as air freight or mountainous regions, and if there is no pressure equalisation between a sealed piece of insulating glass and the outside atmosphere, variations in air pressure result in considerable tension at the edges of the glass and inside the glass itself. This can cause damage to the sealant at the edge of the glass – or even breakage. Air reduces the risk of failure before installation.
Riederalp, Valais in Switzerland is a highly mountainous region, and transportation of sealed units to compensate for the altitude has always been challenging – until a new installation fabricated with Swisspacer Air. The glass had to be transported by mountain railway, and with a difference in altitude of 1,166m above sea level, and a journey time of nine minutes, there was a climb rate of 130m/min in altitude. Swisspacer Air compensated for the climactic load and ensured that the sealed units performed as well in-situ as in the factory.
Air is a simple and reliable component that can be fitted into the sealed unit in less than three minutes by screwing the component into Swisspacer warm edge spacer bars, without significantly impacting on the U-values of a unit. Air has been certified by IFT Rosenheim to prevent failure from atmospheric pressure variations.