Glazing-bar windows are the product of a compromise from the past. Because for a long time the available technology did not allow large panes of glass to be produced, people made do with smaller panes, which were assembled into larger surfaces using glazing bars fitted in between. This provided more incoming light and made it possible to create large, imposing glazed windows or doors. Today it has long been possible to achieve large glazed areas without glazing bars as well. But glazing bars, as a structuring element, still have their justification – with historic buildings in any case, and with modern buildings depending on the style and the way a building relates to its landscape setting.
Large glazed surfaces or structured glazing-bar windows?
Some architects and some clients love large glazed surfaces that are not interrupted by anything. With certain modern building styles this is indeed appropriate. On historic buildings, or on buildings that follow the local vernacular style – particularly in the countryside – windows without glazing bars often look like dark holes, or even wounds in the skin of the houses. Here a sensitive architect will turn to glazing-bar windows that suit the character of a house and that can also lend a house charm. There is no question about the use of glazing-bar windows on listed buildings. Other windows here are often not even eligible for approval.
Different types of glazing-bar windows
Glazing-bar windows no longer actually have to be assembled from several panes today. This is still possible, has its advantages, but also serious disadvantages, particularly in terms of price. Modern technical options open up the opportunity to produce glazing-bar windows more cheaply and almost indistinguishable in appearance from a genuine glazing-bar window.
Genuine glazing-bar windows
With genuine glazing-bar windows, the window surface is still divided by timber, metal or uPVC glazing bars. This has the advantage that, in the event of glass breakage affecting only one of the panes, only that pane has to be replaced. With genuine glazing bars, very professional workmanship must rule out any possibility of them acting as a thermal bridge and thereby reducing the energy efficiency of the window. This is possible, but it makes the window more expensive in any case. With triple glazing featuring genuine glazing bars, it is no longer possible to keep the bars so slim that they match the proportions of historic examples.
Decorative or Helima glazing bar
When decorative glazing bars are used, the window surface is no longer subdivided; the bars are located within the cavity between the panes. After the best-known manufacturer, these bars are also called Helima bars. Fitting decorative glazing bars barely changes the U-value of the windows, so that U-values just as good as with windows entirely without bars can be achieved in a considerably more cost-effective way. In the event of glass breakage, the complete glazing unit always has to be replaced. In visual terms, decorative glazing bars open up many possibilities, as they can be supplied in different colours. Viewed from some distance, they too look like genuine glazing bars; only on closer approach does one notice the illusion.
The Vienna glazing bar
This variant of the glazing bar, also known as the imitation bar, is glued onto the pane. It is the most economical variant of glazing-bar windows, likewise unproblematic in energy terms and barely distinguishable in appearance from genuine glazing bars. Here too, in the event of glass breakage, the entire glazing unit naturally has to be replaced. To enhance the visual effect further, Vienna and Helima bars can also be combined with one another. It is then almost impossible for a layperson to tell them apart from a genuine glazing bar.
The glazing-bar window and the question of aesthetics
Among most people – including architects, window makers and other specialists – there is agreement about the use of glazing-bar windows when renovating and modernising historic buildings. Where glazing-bar windows were previously fitted, glazing-bar windows are usually used again. Often not genuine glazing-bar windows, but those with decorative or Vienna bars.
With modern buildings, opinions diverge more widely. Some architects regard glazing-bar windows as an anachronism that has no place in modern architecture. Others value glazing bars in modern façades too, on account of their structuring effect. Glazing-bar windows are also often used on new buildings that are intended to correspond with a historic building next door or opposite. In rural areas as well – above all in southern Germany, Austria and Switzerland – the glazing-bar window is still widely used in new builds too.
Ultimately, the use of glazing-bar windows in modern architecture is a matter of taste, to be resolved in dialogue between the client and the architect. With today's technical possibilities, window makers can implement almost anything that is desired.
