Light: 75 kg/m2 < p ≤ 125 kg/m2

The Forum Building façade has hardly been discussed, perhaps because it was eclipsed by other buildings in the same area and by other aspects of the Forum Building itself. However, after fourteen years, this risky lightweight solution has been successfully integrated into the city’s landscape. The original electric blue has slightly dulled, at the same time as a salty dust patina has added enriching nuances.

On this occasion, Batlle and Roig resort to a curtain wall in which partial structures are assembled at each slab front without physical continuity between them. Glass panes are then supported over the partial structures to close the façade (have a look at the "Cadireta" curtain wall structure). Each two glass panes are framed with an aluminium frame made of unitized panels profiles. So, is this a unitized façade or a curtain wall one? Maybe it is a mixture of the two?

In the ventilated façade of the Institut Geològic de Catalunya (IGC), the inner layer responds to the window distribution that the use of the building requires and the outer layer responds to formal aspects. The perforated corten sheet that clads the entire façade provides an abstract image, behind which domesticity is solved. The perforated metal sheet shows a drawing and plays with transparencies: it is a rich composition resource that is possible in multilayer façades.

Years after the construction of the AC hotel in the Forum area, the one in Sants was built. The construction solution adopted for the rainscreen façade is practically the same in both cases. Again, a lightweight enclosure is employed when the use demands low thermal mass solutions. Again, a reinforced frame supporting the window is the structure required to release an opening in this unidirectional façade structure.

In this case study, we want to emphasize the construction solution applied on the façades and the roof: an ETICS system coated with ceramic tiles. 

The RBA headquarters are not included here to talk about the project as a whole; an analysis that would allow us to highlight very positive aspects. Instead, our focus is the façade and its lack of sincerity.

The two longitudinal façades of the lower volume are articulated from a grid that reproduces the rhythm of the concrete structure. It is not the true “structure” that we see. The façade enclosure covers pillars and slab edges from the outside, hiding them from sight.

Mecanotubo is one of the façade industries that invested heavily in the late 1990s in Catalonia to provide a unitary response to the rainscreen façade.

They opted to adapt stick curtain wall technology to this two-layer façade. As in the Carburos Metalicos façade, the resulting inner sheet provides enough water tightness to consider a drainage cavity, and consequently an outer layer, unnecessary. Here the outer layer acts only as a covering.

If the inner layer of the rainscreen façade at the Hotel AC was innovative, the proposal for the neighbouring office tower for the Zona Franca Consortium was even more so. Again, the exterior image is a sober stone skin anchored over aluminium profiles. However, on this occasion the inner layer made of boards over steel framing was prefabricated and arrived at the site as panels.

The AC Hotel was one of the first buildings in Barcelona in which a ventilated façade system was used with a light inner layer made of cement boards over metal folded sheet profiles. 

Since then, these systems have evolved to provide a clearer solution regarding  the continuity of the thermal insulation and air tightness. This is achieved by improving the solution in the slab edge and with the adequate treatment of joints. 

Profiled metal trays, which are so common in industrial buildings, find a new use in this residential complex in Guadalajara, Spain. 

Although we greatly appreciate the cleverness and simplicity of the solution, there are problems we cannot deny: thermal bridges through the metal ribs, the lack of water vapour permeability and the compositional limitations derived from the tray width.