Looking at these examples, it can be seen that:
- A TGU can be worse than a DGU
- TGUs can be no better than a DGU
- A 24mm unit can be better than a 28mm unit in both TGU and DGU
- Wider gas filled cavities giving wider over all unit thickness can achieve significant improvements in lowering U-values
- Going from a standard 28mm 1.2 W/m2.K DGU to a 36mm TGU with Planitherm One, almost achieves a 50% improvement in performance
The cost of triple glazing dictates that to achieve overall energy savings, correct triple glazing needs to be specified and wider cavities are required.
A major aspect of triple glazing is that the weight of the glass is increased by 50%. Customers need to be assured that the hinges, fixings and other window/door hardware can cope with this increase. Additionally, the centre of gravity of the glazing has moved and this may put additional stress on the hinges and friction stays.
The window may also look less aesthetically pleasing as the bead that holds the glass in place will be narrower and may affect the overall appearance.