Hanging gardens.

Swathed in lush vertical greenery, this office block makes inventive use of planting to control solar gain.

Lying on a latitude of 33 degrees south (nearer the equator than Seville, for instance), Santiago's climate is intensely hot and dry. Adapting the archetypal Mediterranean practice of mediating between interior and exterior domains, buildings are traditionally organized around cool patio courtyards and wide covered verandas. This extends the habitable realm by providing shade and offering protection from the rain. Adding a further layer of lush visual and physical texture, plant-covered pergolas (parrones) are also used to diffuse light, soften elevations and create shade.

Santiago's Neo-Classical architecture makes exuberant use of parrones and the tradition has been revived and reinterpreted by Enrique Browne in his recent buildings. As well as being ecologically appropriate and environmentally responsive, planted screens are also a highly adaptable and relatively economical means of reducing energy use in buildings. Browne has used planted trellises in several small to medium sized projects (a series of houses, a youth hostel and his practice's recently completed atelier), where parrones fit easily with the modest scale. Realizing such green, humanistic aspirations on a larger scale and in the face of tougher commercial and functional imperatives would always prove a more formidable test of architectural ingenuity. However, Browne, in collaboration with Borja Huidobro, rose to the challenge when presented with a commission for a large office block in Santiago.

Spectacularly framed by the Andes, the eastern sector of Santiago has evolved into the main business district, its urban grid punctuated by office towers from various eras that merge into a nondescript, high-rise skyline. The programme for the Consorcio-Vida offices combines both lettable space and a headquarters for its insurance company client. The building occupies half a block on El Bosque Avenue, which forms part of the regular street grid. At the south-east end of the block, the grid is bisected at a 45 degree angle by Tobalaba Avenue, and the intersection of these axes determined the essential geometry of the building.

Based on a rectangular footprint, the principal street elevation on El Bosque Avenue curves to a prow-like point at its south-east corner. The lowest four floors are occupied by the insurance company, with a further 13 above available for general commercial letting. Both parts have separate entrances and vertical circulation and are unified by a triple-height galleria at ground floor level.

The long east elevation is glazed, with views out to the mountains. The curved west facade is stepped back in three sections, and crowned by a crisply detailed overhanging roof. In Santiago, westerly facades are particularly vulnerable to solar gain and overheating, so the west elevation is protected by an outer screen of planted trellises. Varying between four and two storeys in height, the trellis frames are set around 1.5m beyond an inner skin of double glazed, low-emissivity panels. After some four years, the planting is now fully established, creating a luxuriant green screen that has been calculated to reduce solar gain by 60 per cent. West-facing offices enjoy the benefits of greenery and light magically filtered through the planted trellises.

Like a contemporary version of Babylon's mythical hanging gardens, the sculptural greenery forms a dramatic and original addition to the Santiago skyline. Planting changes with the seasons, animating the curved facade with colour and life. Transforming challenging climatic and urban contexts into a source of creative stimulus, Consorcio-Vida shows that decent environmental conditions can be achieved in a modest, unrhetorical way. And, as the greenery continues to flourish and evolve, it is also a rare example of a building that seems destined to actually improve with age.