Zinc, an unexpected material for transparency

 

 

 

Zinc, an unexpected material for transparency

Using metal rather than glass to give transparency to the building envelope: a contradiction in terms? Architects are increasingly using metal, a dense opaque material, to create more sophisticated forms of transparency with a play on meshes, textures and wall-mounted envelopes.

Zinc – whether it is perforated, scarified or bent – is the perfect solution for this transformation of metal, pushing the boundaries of its versatility. Metallic mantillas, veils, meshes, lace… like a piece of clothing, they hide and reveal multiple realities. Behind the veil, perhaps there is a volume that is identical to the mesh covering it. Or perhaps the mesh creates a complex virtual envelope, its halo covering a building with a very simple form.

The desire for transparency remains highly contemporary. It questions the boundaries between exterior and interior, reveals or dissimulates. Its implementation has become more complex. Ideally, a building with transparent walls displays its purpose, its users and the activities going on inside it. This form of frankness led to transparency being perceived as a constructed expression of democracy. Today, issues have evolved. The initial militant symbolism has subsided. And tomorrow? The ultimate form of transparency will perhaps make it possible to see through opaque materials. For example with concrete or composite materials that are translucent or made partially transparent, or with optical effects via projections on the facade, at the discretion of the occupant, of an image depicting what’s happening inside the building!

Let’s come back to the transparency of zinc and take a look at technical aspects. Perforation of zinc introduces transparency with varying levels of perforation. The choice of level of perforation depends on the aesthetic objective. The latter can be “daytime”, in which case the wall seen in daytime will be perceived as more opaque and the perforations will form a visible motif. There is another aesthetic objective called the “night-time” objective, whereby the interior lighting makes the perforated wall disappear at night-time, allowing the heart of the building to become visible.

Transparency of zinc is possible with a low rate of perforation (30%). So it is not necessary to remove a lot of material to obtain transparency. By modulating the size and distribution of perforations, the architect varies the degree of translucency of the building envelope to make it play different roles, such as the sometimes very sophisticated role of sun-screen.

To reduce the inevitable visual presence of the framework behind the envelope, the rigidity of the zinc panels is reinforced with customised folds. This reinforced inertia ensures larger spans (usually the height of a storey). The combination of these bends with the perforations enriches the texture of the facade with multiple shadow effects that make it vibrate.

Zinc is the ideal material for perforated metal panels, as the sheared edges of the perforations will develop a natural patina over time. The surface of the zinc develops a self-protective dark grey coating that gives it an exceptional lifespan (forty years in aggressive urban areas and up to one hundred years in protected rural areas).

There is a world of difference between installing a sheet of zinc on a traditional roof and installing the same sheet, perforated, on a contemporary facade. In the first case, even the smallest hole is a defect in terms of watertightness and a source of shame for the installer. In the second, multiple holes allow water, air and light through the zinc and are a source of satisfaction for the architect! This is the kind of comparison we like because it expresses the evolution of the material and its uses.

Roger Baltus
Engineer - Architect
VMZINC Communication Director

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