Glazing edge at the highest level

Study shows: high-end solution from Dow and SWISSPACER enhances façade performance

Kreuzlingen, Switzerland - 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. Now, a joint study initiated by sealant expert Dow and SWISSPACER – the specialist in warm edge spacer bars – 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.

“Warm” secondary sealant with numerous advantages

The idea for the jointly initiated study, carried out by the renowned engineering firm Bauwerk (Rosenheim), came about in the course of product development. At Dow, the focus was on the patented silicone technology presented at glasstec in 2018, DOWSIL™ 3364 Warm Edge IG Sealant.

Aluminium profile (ift guideline) 100 mm, triple glazed 40 mm

Simulation model (detail) with SWISSPACER Ultimate (isothermal lines at 0°C externally)
Um = 1.1 W/m2K / bm = 50.0 mm / Ug = 0.7 W/m2K

Integrated in the triple glazing of an aluminium façade design, DOWSIL™ 3364 in combination with the SWISSPACER Ultimate achieved a value of 0.846 W/m2K. In comparison with a conventional PU sealant and the stainless steel spacer bar, the overall energetic performance of the high-end solution is over 15 percent better.

The innovative secondary sealant for gas or air-filled insulating glass with multiple panes has up to 45 percent lower thermal conductivity (λD = 0.19 W/mK) than conventional insulating glass silicone. With organic sealants, such as polysulphide or polyurethane, that value increases to as much as over 50 percent. At the same time, depending on the design of the façade and the façade system used, the new edge seal silicone allows for up to 25 percent lower Psi values in warm edge designs. Another advantage: DOWSIL™3364 increases the surface temperature on the inside of the glass by up to 1°C, thus reducing the risk of condensation and the formation of mould. The silicone, which is approved according to the European Directive for Structural Glazing (ETAG 002), shines in particular when it comes to its high adhesive strength, temperature resistance up to +150 °C and its UV stability.

The innovation leader SWISSPACER has the best warm edge spacer bars on the market. Together with its partners, the Swiss company regularly develops new technology solutions, which contribute significantly to tapping into the full potential of highly energy efficient window and façade solutions.

DOWSIL™3364 and SWISSPACER Ultimate – for significantly lower heat losses

Within the framework of the present study, different façade designs were studied with a conventional Polyurethane (PU) sealant, a standard silicone sealant, as well as DOWSIL™ 3364 – each combined with a stainless steel spacer bar or the SWISSPACER Ultimate. The results are clear: For example, DOWSIL™ 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: 1x2 m) achieved a Ucw value of 0.846 W/m2K – this means a heat transmission coefficient that is over 13 percent lower in comparison with the use of a stainless steel spacer, which achieved a Ucw value of 0.976 W/m2K. 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.

Schüco FW50+SG profile, triple glazed 40 mm, with toggle system

Simulation model (detail) with SWISSPACER Ultimate (isothermal lines at 0°C externally)
Um = 1.1 W/m2K / bm = 50.0 mm / Ug = 0.7 W/m2K

Schüco façade system FW50+SG with glass anchor (element size: 1.0 x 2.0 m) and triple glazing (40 mm): When using DOWSIL™ 3364 in combination with the SWISSPACER Ultimate, the design reaches a Ucw value of 0.915 W/m2K. When using a conventional silicone sealant and stainless steel spacer bar, the Ucw value amounts to 1.051 W/m2K – a difference of 13 percent.

Particularly impressive in terms of condensation: In comparison with the conventional sealant and a stainless steel spacer bar, the combination of DOWSIL™ 3364 and SWISSPACER Ultimate 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%), condensation forms with this set-up only from an outside temperature of -49°C.

More room for manoeuvre in façade design

Dow and SWISSPACER were greatly satisfied with the results of the study. Karl-Theo Roes, Head of Market Development and Innovation at SWISSPACER, explains: “The study demonstrates with clear figures that the sealant and spacer bar, which are components that are often neglected when looking at energy aspects, have an enormous impact on the energy efficiency of a façade structure. At the same time, they can reduce the risk of condensation and thus increase comfort. This allows designers and façade builders even more room for manoeuvre, particularly when it comes to designing and executing high-performance façades.”
Markus Plettau, Marketing Manager High Performance Building, EMEA at Dow, adds: “With our 'warm-edge silicone' DOWSIL™ 3364 and the SWISSPACER Ultimate in all-glass façades with a toggle system, Ucw value improvements of up to 0.14 W/m²K are possible without a design change. The reduction of the CO2 emissions of the property associated with improved energy efficiency can be considerable. A sustainable system all round."

New and attractive solutions are presenting themselves to metal manufacturers and smaller façade construction companies: all-glass façades with U-profiles ("toggle systems") are particularly suitable for small and medium-sized façades, as they are simple and cost-effective. Combined with the performance of DOWSIL™ 3364 and SWISSPACER Ultimate, they also boast excellent energy efficiency.

Building owners, architects and designers will be pleased to know that costly design changes or façade insulation will in many cases not be required. Energy efficiency and condensation problems with complex façade geometries, all-glass corners or filigree all-glass designs can be addressed in the long term with this powerful system.


The study and further information are available for download on the websites at and

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Photos are available for download at

SWISSPACER is the pioneer behind warm edge spacer bars all around the world. The company was founded in 1998 and is part of the Saint-Gobain Group. SWISSPACER products stand out thanks to their excellent functional and aesthetic properties. The company's headquarters with production, R&D and administrative offices are located in Switzerland. There are further production sites in Germany and Poland.

About Dow
Dow (NYSE: DOW) combines broad technological expertise, in-house production plants, focused research and development and global reach and thus relies on profitable growth to become the most innovative, customer-focused, inclusive and sustainable material science company. Dow’s portfolio is comprised of the segments Performance Materials, Industrial Intermediates and Plastics and offers customers in high-growth industries such as packaging, infrastructure and consumer goods a wide range of differentiated, science-based products and solutions. Dow operates 113 production sites in 31 countries and employs around 37,000 staff worldwide. In 2018, the company generated turnover of around USD 50 billion (pro forma). References to "Dow" or "the Company" mean Dow Inc. and subsidiaries of Dow Inc. For more information, visit or follow us @DowNewsroom on Twitter.

Further information:

Janina Brielmann
SWISSPACER Vetrotech Saint-Gobain (International) AG
Sonnenwiesenstraße 15
CH-8280 Kreuzlingen

Markus Plettau
Dow Silicones Deutschland GmbH
Marketing Manager EMEA
High Performance Building - Consumer Solutions
Rheingaustrasse 34,
D-65201 Wiesbaden