Against the background of constantly increasing demands on the energy efficiency of glass façades, the focus is increasingly shifting towards the glazing edge of insulating glass with multiple panes and structural glazing applications in particular.
Because while the U values of the glass itself have little left to optimize in terms of efficiency, there is still significant potential in the sealants and spacer bars used. So sealant expert Dow and SWISSPACER – the specialist in warm edge spacer bars – initiated a joint study on this. The study, carried out by renowned engineering firm Bauwerk (Rosenheim), shows: an optimal combination of the sealant and spacer bar can improve the Ucw value of a façade by more than 15 percent – without changing the façade design.
DOWSIL™ 3364 and SWISSPACER Ultimate – for significantly lower heat losses
Within the framework of the study, different façade designs were studied with a conventional Polyurethane (PU) sealant, a standard silicone sealant, as well as the patented silicone technology DOWSILTM 3364 Warm Edge IG Sealant – each combined with a stainless steel spacer bar or the SWISSPACER Ultimate.
The results are clear: For example, DOWSILTM 3364 in combination with the SWISSPACER Ultimate in a piece of triple glazing (40 mm) as part of an aluminium façade design (100 mm profile depth, element size: 1×2 m) achieved a Ucw value of 0.846 W/m2K – this means a more than 13 percent lower heat transmission coefficient in comparison with the use of a stainless steel spacer bar. With a conventional PU sealant and the stainless steel spacer bar, the same façade design achieves a Ucw value of only 1.002 W/m2K – the overall energetic performance of the high-end solution is therefore about 15 percent better.
In comparison with the conventional sealant and a stainless steel spacer bar, the high-end solution also results in a temperature on the inside of the glass that is 2 degrees higher. In a normal climate (room temperature 20°C and relative humidity 50 percent), condensation forms with this set-up only from an outside temperature of -49°C.
More room for manoeuvre in façade planning
An advantage for metal manufacturers and smaller façade construction companies: all-glass façades with U-profiles (“toggle systems”) are suitable for small and medium-sized façades, as they are simple and cost-effective. With the performance of DOWSILTM 3364 and SWISSPACER Ultimate, they also boast excellent energy efficiency.
Building owners, architects and designers will also be pleased to know that costly design changes or external wall insulation will in many cases not be required.