Hot issues. (Comment).

Building in hot latitudes presents its own particular challenges, but even the most extreme climates can give rise to intuitive forms of architecture that have an important role to play in the search for a new ecological responsiveness.

Around 7.5 billion years from now, the sun will finally exhaust the source of hydrogen fuel in its core and swell monstrously to become a red giant, whose fiery surface will engulf our Earth and the inner planets. Oceans will evaporate, rocks turn to molten lava, and if organic life (plants, animals, humans) still remains, it will be swiftly extinguished. Should the Earth survive being incinerated (astronomical and scientific opinion varies on this point), it will then become a dark, airless, frozen cinder as the sun enters the final stage of its star life, cooled and transformed into a dense white dwarf. From our insignificant vantage point in the evolutionary cycle, it is momentarily sobering to reflect that the life-giving source of light and heat, venerated and worshipped over millennia, is destined to become our planet's fiery, hellish nemesis.

Heat from the sun kick-started human civilization--the first hominids flourished amid the warm, equable climate of the African savannah, with no need for shelter, a kind of primordial Eden. Fire, clothes and buildings came later, as primitive humans gradually colonized different climate zones. At present, arid and semi-arid regions occupy just over a third of the earth's total land area, but neglect and mishandling of ecosystems adjoining desert regions are transforming vast stretches of sub-humid and semi-arid land into sterile wildernesses. In Africa, for example, agricultural land is being consumed by the Sahara to the north and the Sahel to the east.

Equally alarmingly, indications continue to suggest that the temperature of the earth is slowly rising as a direct consequence of increased emission of greenhouse gases in the atmosphere, notably [CO.sub.2] and methane. Rising sea levels, thinning ice caps, melting glaciers, expanding deserts, earlier springs in the northern hemisphere and extreme heat episodes in hitherto temperate climate zones are all manifestations of this phenomenon. While we are not yet in danger of being fried to a cosmic crisp, things are definitely hotting up.

Too much sun can precipitate environmental and social catastrophes, such as drought and famine, and within our precariously small zone of temperature tolerance, excess heat can be lethal. If an adult human being were to stand naked in the Sahara (where temperatures can easily rise to 49 deg C), he would lose most of his body water by midday. By late afternoon, his glands would stop functioning, raising his body temperature to 42 deg C. Soon after this, he would die (if not provided with water) and expire even quicker if exposed to the desiccating effects of hurricane winds (completely dried and mummified bodies have been found after desert sandstorms where individuals were unable to get help or water).

Survival tactics

Despite the harshness of such conditions, humans have developed many ingenious means of survival in hot latitudes. The lightweight goat hair tents of the nomadic Bedouin, for instance, can be pitched under a tree for shade, or to catch prevailing breezes. Australian aborigines build open-sided willja, shelters covered in paper-hark which permits air circulation yet gives dense shade. The Acoma Indians of the American South-West constructed thick-walled adobe dwellings which absorbed the heat of the day and released it at night, fundamental principles of thermal mass now reinterpreted in contemporary approaches to environmentally responsive design.

Beyond the level of mere survival, there are numerous examples of inventive building types developed in response to hot climates, The basic Arabic and Persian courtyard house, with rooms arranged around an open often planted or water-filled courtyard, is a common feature of life from Morocco to India. In the hot, humid conditions of the Asian tropics, buildings are traditionally elevated above ground, with overhanging eaves and thin permeable walls to encourage ventilation. In their conquest of Mexico and South America, the Spanish adapted Mediterranean principles to more challenging climes, with their haciendas, adobe patio houses and city squares or zocala. In Australia, the prefabricated timber and tin verandah houses of the Victorian era were layered, lightweight and in contact with nature, principles that still obtain in the work of contemporary Australian architects such as Glenn Murcutt and Bligh Voller Nield (p48).

In modern times, such intuitive, ecologically undemanding ways of living and building in hot climates have been superseded by the rise and rise of technology, notably air conditioning. The outcome is that from Dallas to Dubai, models developed in temperate climates, such as the glass curtained, air-conditioned, energy-guzzling office block are simply plonked down in patently unsuitable settings. This 'one-size-fits-all' approach has its roots in simple economic expediency but also, to some extent, in the heroic, progressive visions of Modernism (despite Corb's discovery of the brise-soleil). In an age of increasingly rapacious globalization, this lowest common denominator thinking has also been reinforced by a more general erosion of regional identities and cultural nuances. Yet it is clear that long held tenets of vernacular wisdom are still relevant if we are to evolve new climate-specific planning and building models - and ways of construction--that will create environments that are both ecologically sust ainable and humanly satisfying.

The buildings in this issue attempt to show how architecture is shaped and tempered by hot climates--from the unforgiving latitudes of Chile's Atacama Desert, p42 (the driest inhabited place in the world), to a new language of tropical Modernism in Singapore, p54. All in their different ways add to the ongoing debate and the perpetual search for appropriate models that try to touch the ground lightly. In doing so, the experiential dimension of hot climate architecture should not be overlooked. Unlike cool climates, where elements have to be firmly repelled through a protective, impermeable enclosure, buildings in warmer latitudes are usually more open and can filter the climate in many different ways, enriching the relationship between architecture and context and bringing humankind in touch with nature in a way that is both pragmatic and poetic.