The urban planning that provides the context for the Eix Macià, the great traffic, commercial and residential axis built in the late 1980s to promote the urban and economic development of Sabadell, was based not just on the usual regulating parameters (layouts, areas, occupations, heights, etc.) but also and most particularly on the specification of specific volumes that aimed to control the resulting urban form and, accordingly, the character that this city fragment
was to acquire. The specification of a variety of volumes (long low blocks, cubic blocks, screen blocks and towers) set out to draw in the city’s skyline the same as was planned for its structure, growth and economy: a new urban model. In this new skyline, the tower form had to be precisely gauged to adapt to the logical moderation of a city like Sabadell, where the tallest construction had hitherto been the bell tower of its main church. To ensure the appropriate proportion, the floor plan of the tower had to be reduced to a minimum to ensure the desired slenderness, to the extent of distorting the initial square to produce a rectangular form that turns its shorter side onto the main avenue.
The project for the Millenium building came into being with certain decisions already taken at the urban implantation stage (alignment in relation to the street, size of floor plan, length of faces and height). In most buildings, these decisions are taken by the person responsible for the design, giving rise to a single discourse that competently draws together place, form and programme. Yet after a few work sessions, the not entirely pleasant feeling of jumping on board a moving train, joining a project that had already begun, gave way to the surprise of discovering that a building is, in itself, capable of structuring a specific discourse, over and above its appearance, and that once the more circumstantial—and also most trivial—initial questions had been answered (What should it look like? What shape should it be?), the really fundamental ones had to be addressed: what is it? How does it work?
So, what is a high-rise building, and how does it work? Thinking about the functioning of a building with 20-something storeys means thinking about vertical transport: of people, obviously, but also of energy—that is, water, electricity, air and everything else needed to implement the programme. A high-rise building is an energy structure associated with a vertical system of storage and transport, and what might seem a utilitarian definition became the waybill for developing the project. To start with, where should the energy be created and stored? High-rise buildings habitually use the roof to accommodate cooling machines, fuel tanks and electricity converters and distributors, as these installations need ventilation, though in a worst-case scenario they may be divided between the roof and the higher basement floors. Ruling out this possibility, discussion centred on the contradiction of using what is, ultimately, the most privileged place, the top, for a use that is very important functionally but offers limited access. In addition, the vertical layout of installations highlighted a degree of duplicity in both the length and diameter of transport elements. With regard to the location of energy production and storage in the building, careful attention to fire regulations provided the information needed to make the final decision. A high-rise building must have a central area to serve as a firebreak between the upper and lower floors that is ventilated and insulated from them by fire-resistant protection.
We therefore thought of a solution that involved situating the installations at an intermediate level in the building and discovered that this simplified diameters and volumes of flow, and routes and lengths of layouts, while providing correct insulation in the event of fire. Once this decision had been taken, the building acquired a typology of its own. The need for ventilation of this floor called for a façade skin that allowed the interior to breathe. Having devised a way to allow the mechanical floor to breathe, we could then ventilate all the floors to the exterior, almost removing the need for interior ventilation conduits. The building ceased to be a “chimney”, a vertical structure through which the ventilation elements rise to a single outlet at the top, and became an “arm”, a long element that ventilates through its entire surface by means of many tiny pores. This led to a discussion about this breathable skin and its permeability, tension, fragility and hardness. It seemed to us that the key lay in making it independent of the supporting structure. If the two were totally associated, it would be difficult to give the envelope the fragility needed to make it easily permeable. Even an ambiguous relation of relative proximity would make it difficult. We decided to separate the facing as far as possible from the structure, creating a 3.60-metre projection from the first line of columns right round the perimeter.
The directions taken and the decisions made thus far as to the location of the building’s energy production, storage and distribution, and the way this influenced the envelope and, in turn, the structure, informed the new working scenario. Leaving behind problems arising from form and urban planning requirements, the building acquired values of its own to bring to the design process. From this moment on, the decisions taken and the important details were based on a discussion of energy, structure and envelope: the choice of a metal-sheet curtain wall in which the opaque and the glazed surfaces shine equally brightly, but without merging; the limitation of the area occupied on the ground floor in an attempt to recover the alignment of withdrawn columns and close the envelope one floor above the street, further emphasising its lightness; the rounded corners give continuity to the four façades, further tensing the surface and challenging the specific proportion of each side; the variability in layout of the glazed and opaque parts suggests that the building had been previously used and the logical order of its openings interfered with; and, finally, the vents that serve to aerate the floors, like small pores, along with the great eyes at the top of the tower, which serve to remind us that the ultimate function of a watchtower is merely that of looking.