Insulating glass – a more lightweight triple unit
It is possible to assemble triple IG-units considerably lighter in weight using heat-strengthened thin glass as the middle sheet. Tempered or heat-treated thin glass has a very high mechanical load capacity, is very flexible but very light in weight and therefore ideal for triple IG-units. LiSEC already tested and introduced various pane constructions using thin glass instead of common 4 mm (or thicker) float glass sheets. As a result, not only the unit’s weight was reduced but also the problem of climate loads was controlled in a better way.
One possible construction consisted of one exterior 4 mm float glass sheet, one heat-strengthened 2 mm centre pane and one interior 3 mm float sheet with Argon gas filling. At a weight of only 22.5 kg/m2, a Ug-value of 0.6 W/m2 and light transmission of 73% would be reached. Total energy transmission would amount to 61% and therefore be comparable to a double unit. Also sound insulation would be of equivalent quality because of the sheets’ different thicknesses.
Because of the membrane effect of the flexible, tempered thin glass in the unit, there is very low pressure inside which results in low tension. Even if the glass was exposed to high temperature changes, fluctuations in pressure would be compensated within the unit. Therefore it can almost be excluded that the glass brakes.
As thin glass shows a very specific elasticity, the load at the edge sealant of the unit is reduced even for wide spaces between the sheets. Also optical distortions were reduced substantially. The sheets are coated either on surfaces #2 and #5 or on surfaces #3 and #5. The only drawback left is that triple units are thicker. Thinner units showing equal Ug-values can be assembled using krypton. These are quite costly, though.
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