ENDESA HEADQUARTERS, MADRID, SPAIN

architect
Kohn Pedersen Fox—Lee
A. Polisano, James E. Outen, Cristina
Garcia, Eliseo Rabbi

The eight-story atrium at the center of this corporate headquarters is actually a kind of condenser, combining aspects of identity, urbanity, and climate control in much the same way as the traditional patio in southern Spain does. The spreading table of its shade roof offers a ready corporate identity. Its main floor, surrounded by services and overlooked by the changing drama of light filtering through the roof’s louvers and struts, brings a measure of urban intensity to its suburban setting. And with its sophisticated control of sun, heat, and air, it makes effective use of the traditional patio’s climatic benefits, offering a model for office-building energy conservation. This last is a particularly appropriate feature, since Endesa is one of the country’s major electric producers.Program In the Campo de las Naciones business park outside Madrid, the building brings together the 1,300 employees and various divisions previously scattered around the city. Its 370,000 square feet of office space and 240,000 square feet of lower-level and basement services “creates a more efficient and interactive working environment,” as √Kohn Pedersen Fox’s (KPF) brief explains. (KPF’s London office designed the building with Rafael de La-Hoz, a Madrid-based architect specializing in corporate buildings.) The company initially expected to fill the facility gradually, leasing what it didn’t use, although in the end it occupied the entire structure. The project had to create a strong identity for Endesa on a limited budget (the total cost, according to La-Hoz, was $81.6million). Horizontal slats of fritted glass protect the southern and western exposures of the imposing block that faces the highway, reducing glare and noise. This block folds around the atrium to the south to create the executive office wing, and angles out at its northern end in a 100-foot-long cantilever, a gesture that commands attention from drivers zooming by on the highway (and conveniently avoiding foundations in poor soil, according to Polisano). Inside, corridor bridges span the atrium, dividing it into an entry court, a central gathering space, and a multilevel zone for work breaks and informal meetings at its northern end.The large roof deck is a layered fifth facade, supported by a gangly structure of tubular steel legs and 17 trusses with spans of up to 120 feet. Mounted on the trusses, motorized aluminum louvers performing the role of the traditional patio’s movable canvas tarp over the atrium. (The client ultimately rejected the architects’ proposed arrays of photovoltaic cells.)
The continuous plane of glass over the atrium is the largest and most technically challenging glazing installation of its kind,according to the architects. Each glass sheet, about 4.5 feet by 9 feet, hung from the trusses, can support the weight of maintenance workers. The glass roof pitches for drainage, is acoustically sealed, and engineered for fire-resistance. Despite this complexity, its overall effect is light and direct. Polisano comments, “We all worked very hard to get that.” Exploiting the wide temperature swings in hot-climate Madrid, the underfloor ventilation system uses cool nighttime air to draw off heat accumulated in the slab during the day. Exterior windows were sealed for budgetary and acoustic reasons, but exhaust air flows naturally into the atrium from the slightly pressurized offices. Heat gain from the glass roof and four passive-solar chimneys induces exhaust air to rise, improving air circulation. An evaporative system delivers free cooling from the ground through the atrium floor, augmented by mechanical cooling when necessary.The dramatic atrium changes its mood with the shifting of roof louvers and the moving clouds and sun. Despite this grand public gesture, the atrium feels oversized at ground level, and it lacks the hoped-for buzz of activity. Security measures keep the general public out—as would the isolation of the site to pedestrian traffic in any case—and the café tables and landscaping the architects envisioned have failed to materialize. The atrium feels more like a religious cloister, an inward-looking space of retreat and meditation, than one of southern Spain’s livable residential patios.