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Today, the exorbitant energy price increases triggered by the war in Ukraine, the coronavirus-related supply bottlenecks and the tense supply situation have catapulted the energy optimization of buildings back to the top of the agenda in legislation and the construction industry. What can warm edge spacer contribute to this effort? Modern thermal insulating glass units achieves up to 0.5 W/(m²K) as triple glazing with thermally optimized glass edge. A recent study shows that the average Uw value for the most recently reported period between 2017 and 2020 is still far from the passive house standard, which requires triple glazing with a thermal transmittance lower than 0.8 W/(m²K). There is therefore considerable potential in the thermal optimization of insulating glass units. In this context, the warm edge is the solution that is easiest to implement and requires neither complex coatings nor changes in the profile construction.

 

It has long been known that conventional aluminum spacers form thermal bridges in the edge seal, through which valuable thermal energy is lost. Furthermore, in winter, when there are large temperature differences between inside and outside, the glass surface in the edge area of a window with a warm edge is significantly warmer, with the immediate consequence that condensation hardly forms and the comfort in the room noticeably increases. So why do many window manufacturers still rely on aluminum? On the one hand, the reason lies in the price competition, but in part is also due to some in the market not yet fully realizing the extent that the conductivity of an insulating glass spacer in the edge seal also determines the thermal insulation values of a window. The heat loss is quantified by the Psi value Y, a linear heat transfer coefficient measured in the unit W/mK. It describes the heat loss per meter of thermal bridge per degree of temperature difference. With the different warm edge spacers, the values are close together. In comparison to an aluminum spacer however, the impact is clear.

 

 

The warm edge insulating glass represents a technically mature product for a highly competitive market, that is characterized by low margins, a shortage of skilled workers and cheap imports, and also currently by supply bottlenecks and rising material costs. With a thermal conductivity of only 0.15 W/mK, silicone foam has a thermal conductivity 1,000 times lower than aluminum. The additional price for Super Spacer® is in the low cent range per linear meter. The price argument is therefore easy to refute. Furthermore, automated insulating glass production with robot-assisted spacer application offers additional savings potential on the processing side. Flexible spacers from the roll are already prefabricated to the desired width and color. While a roll is running on the applicator, the software signals six meters before the end of the run which material is needed next, and this can be loaded onto the second applicator head. There is no waiting time for the material and the roll change in the applicator is also done quickly: the two ends are connected with the help of an adhesive foil and production can continue. Since flexible spacers are already equipped with desiccant, vapor barrier and acrylic adhesive, there is no need for time-consuming, labor-intensive, and machine-intensive preparatory work. What are the benefits of the warm edge in terms of thermal insulation and heating costs? As a rule of thumb, a difference of 0.04 W/mK in the Psi value means an improvement of 0.1 W/mK in the Uw value. 

 

Super Spacer® structural silicone foam design makes the edge seal flexible, cushions the pressure on it so to speak and the risk of breakage for the glass is significantly reduced. Less stress in the edge seal results in an improved seal tightness and durability of the glass units. The full or partial offsetting of the loads acting on the edge seal is an advantage that especially desiccant integrated pre-formed flexible spacers, such as Edgetech Super Spacer® TriSeal, can claim to possess by comparison with rigid spacers. The manufacturer proves the material properties by means of corresponding tests. Edgetech/Quanex have tested the shear load capacity. An insulating glass unit measuring about 6 x 3 meters wide and 6 mm each thick, was only bonded by means of the integrated primary, high-strength acrylic adhesive. The unit was lifted on one supported glass lite using vacuum cups and the spacer did not give a single millimeter during the 30 minutes test phase. The test demonstrates that the additional adhesive layer reduces the stress on the primary PIB seal, which thus functions exclusively as a water vapor and gas barrier to the secondary seal.

 

Insulating glass lines which are more than 100 m and are capable of processing oversize pane formats are making ever larger and more complex insulating glass and therefore applications such as structural glazing facades are technically and economically feasible. The further development of automatically processable insulating glass spacers as well as application machines has contributed significantly to the XXXL trend. According to the permitted tolerances for the parallelism of the spacer placement to the straight glass edge, a deviation of 4 mm is allowed up to an edge length of 3.5 m. For longer edge lengths, the maximum deviation is 6 mm. For window sizes exceeding the standard 3,210 mm × 6,000 mm band size, assembled rigid spacer frames are difficult to handle due to their lack of stability and their tendency to deflect. The spacer frame must be applied to the first pane in such a way that, on the one hand, it is straight and squarely connected to the glass and, on the other hand, it does not touch it before the final position is found, otherwise the critical PIB edge seal, as well as the sightline aesthetics will be compromised. Flexible spacers are applied robotically from the roll on partially or fully automated lines. For manual processing, Edgetech offers a specially designed hand application tool for Super Spacer® which enables the same precise placement. Since the desiccant is already included in the spacer material, the time-consuming filling of spacer frames is also eliminated. And last, but not least, there is no longer any risk of PIB residue, stains or fingerprints getting into the unit. The shear strength, i.e. the integrity of the entire insulating glass unit, is ensured during production by the interaction of several factors: a sufficiently dimensioned sealant depth, the adhesive force of the spacer and PIB seal on the glass, and the compression during gas filling of the cavity. 

 

The excellent adhesive force of Super Spacer®, even with large-format panes, was demonstrated in a shear load test. Super Spacer® however, due to its flexible foam-based material accommodates the movements countless times thanks to its 100% resilience. If thermally separated composite profiles or structural glazing constructions are heated on one side on the outside due to solar radiation, the thermal linear expansion leads to permanent differential movements and thus a shear stress between the two panes. Frame material made of metal further intensifies this so-called ‘bimetallic effect’ derived from electronics. Rigid conventional spacers cannot compensate for the resulting loads. For this reason, almost the entire shear load here rests on a very thin PIB layer (butyl primary sealant) and on the spacer's adhesion to the outer sealant, which, as mentioned above, can cause it to move into the visible area. A flexible spacer is able to absorb this mechanical stress by dividing the forces among many local forces. The adhesive forces on the back of the spacer, the primary seal, and the additional acrylic adhesive applied to the sides of the spacer hold it in position and prevent the edge seal from being damaged and avoid all the familiar consequences such as gas loss, condensation, clouding, and ultimately a shortened service life. 

 

 

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Edgetech Europe GmbH, located in Heinsberg, Germany, is a fully owned subsidiary of Quanex Building Products Corporation, (NYSE: NX) a global, publicly traded manufacturing company primarily serving OEMs in the fenestration, cabinetry, solar, refrigeration and outdoor products markets. Edgetech Europe GmbH services markets in continental Europe with a total of 490 employees and 17 extruders. We are "A Part of Something Bigger" by improving the performance and aesthetics of end products through continuous innovation, helping customers achieve greater production efficiencies, and giving back to communities where we operate.