Letter to the Editor - Rigid or flexible warm edge spacer bars


Dear Ian,

In his recent report on the Window, Door and Conservatory Markets in Housing, Palmer identifies significant growth and opportunities in bi-folding doors, and highlights growth in patio doors. Strong forecasts of sales growth mean greater demand for larger sealed units in bifolds and sliding patio doors.

But, some have asked, what sort of spacer is best suited to these large units, soft and flexible or a rigid spacer bar? Do heavy window and door frames put more pressure on sealed units, so they deflect, making a flexible spacer bar better at dealing with the deflection?

But it’s not a question of soft or rigid. It’s not the job of the window or door to support the weight of the building above, nor the job of the sealed units to support the weight of the window or door; still less the job of the spacer bar to support the sealed unit, door, window or masonry above. If we built like that we’d all be living in piles of rubble from collapsed buildings!

Appropriately sized lintels are fitted above door or window openings to support the weight of the masonry and building above. They don’t rely on the windows or doors to support the building. Structural engineers calculate the load above precisely and, with a good safety margin, specify the strength and size of the lintel required to support the frame. If they didn’t, the building would fail regulatory requirements, and probably fail itself. Property owners would rightly be concerned!

A window or door frame is strengthened with reinforcement to support its functioning and its own weight. Correctly constructed, the sealed unit withstands lateral movement in production, transit and handling during installation so it performs as designed for its lifetime.

A warm edge spacer bar is designed to keep the panes of glass apart, provide structure and surface for the primary and secondary sealants, and hold the desiccant. They are also a crucial insulating barrier for energy efficiency. It’s the secondary sealant’s job to keep the unit’s structure together and bear the load in production, transit and installation, and withstand the wind loading once installed.

Rigid warm edge spacer bars like SWISSPACER are designed for large IGUs. They give precise edges and clean, crisp parallel lines for an aesthetically pleasing finish. They’re strong enough to cope with the weight of the extra glass without modification. You can see warm edge rigid spacer bars in action worldwide in large sealed units in very exposed conditions e.g. New York’s iconic Museum of Modern Art (MOMA), London’s 30 St. Mary Axe (The Gherkin), The Prada building in Tokyo, Madrid’s Torre de Cristal and The Turning Torso in Sweden all have SWISSPACER inside. Rigid warm edge spacer bars work well in these buildings, so I don’t think Mrs Brown will have a problem with her bifolds!

Yours,

Karl-Theo Roes
Head of Market Development, Europe, SWISSPACER


Company Overview for:

Swisspacer

Formed in 1998 Swisspacer is part of Saint-Gobain Glass Solutions. The company has experienced massive growth in the UK over the past 2 years. Its no-investment needed price benefit has been a key advantage that has attracted sealed unit manufacturers and window fabricators and fuelled its growth.

The manufacturing and head office is in Switzerland and a second manufacturing facility is established in Germany. Much investment is taking place to expand production capacity to ensure that Swisspacer is able to satisfy the dramatic ongoing growth in demand for its high performance warm edge spacer bar products.

Swisspacer has a growing network of leading sealed unit manufacturers in the UK and Ireland using its products, including Solaglas, Pilkington, Carey Glass, Supaseal, Custom Glass, Uniglaze2, Glass Systems, Clayton Glass, System 3 and Hollow Seal among others.

Swisspacer exactly matches the shape and dimensions of aluminium spacers, and being rigid and self supporting it handles in a similar way. And because there is no need to invest in expensive new machinery, it makes it very easy to get up and running with warm edge. Automated solutions are however available from Lisec, Saint-Gobain Seva and Rottler and Ruediger.

Independent tests conducted by IFT Rosenheim, the leading European independent fenestration research and test facility, showed that Swisspacer V had the best PSI values of all the other leading brands of spacer bar that were submitted for testing. Using Swisspacer thermal insulation (U-value) can be improved by up to 20%. Swisspacer V and Swisspacer perform very well in the Window Energy Rating Scheme.