As people were gradually forming their first civilizations, the part of the world we now know as the Sahara desert was lush and cooler, with vast grasslands and other areas covered by woodlands. But then, with dramatic effects, the climate changed. By 4000 years ago, one result was the rapid desertification (perhaps in as little as a couple hundred years) of that northern Africa region. Not merely northern Africa, but almost the entire Middle East has since been dealing with dry, hot conditions. While this circumstance may be a cautionary tale for folks concerned about swift alterations now occurring worldwide, a positive consequence of that ancient shift has been that the cultures of the region have had a long history of responding to baking hot weather. In the process, they have evolved some surprisingly effective and low-energy ways of dealing with the kind of heat that could be more widespread in coming decades.

Just as, while much of Europe was enduring and then beginning to come out of the Dark Ages, Islamic cultures retained great libraries, seafaring skills, the compass, a medical science quite advanced for the time, and sophisticated systems of mathematics, treasures of learning which they would pass along in time to the West, so now, as energy-intensive air-conditioning methods might no longer be as practical as they appeared prior to global warming, the Arabic/Islamic world may again have important things to teach us, this time about how to cope with a world becoming too hot and too saturated with high energy solutions.

An ancient "innovation" that could be useful in many modern buildings is the wind tower. First incorporated in structures of the distant past, yet still in use in Dubai and elsewhere in the Middle East, a wind tower in its simplest form is a vertical, chimney-like tunnel through the roof, connecting air above with air in the room below. But in this "chimney" there are normally four sides, each catching air from one direction and shunting it down to (or up from) the room underneath. Some models have plastic covers or louvers to protect from rain getting in. There is also a roof above. Partitions inside the four tube-like openings keep the air flowing a particular way. Essentially, when the air blows, from whatever direction, part of it is caught in a portion of the wind tower and directed down on that side to the room (or level of the building) below. Because of the temperature (and sometimes humidity) differences, air is drawn in one side from above and out the other, mixed with air from below. Thus, cool air replaces warm air in the room. In certain instances, evaporation may aid convection to lower temperatures. It sounds counterintuitive, but it works! The living space below becomes quite a bit cooler than the prevailing outside temperature. People who have experienced this have described an outside temperature sometimes 50°F above that of the room beneath the wind tower, with no motorized appliances whatever.

Image source: Wikimedia Commons

A second of these techniques is the qanat architecture of ancient Persia (modern Iran). A qanat is a system, usually underground, of husbanding and utilizing fresh water to best advantage, often in areas where it is scarce. Such systems may take many forms and have multiple purposes. Relevant to this essay are the cooling techniques (either for air-conditioning or ice storage) associated with them. However, just as with naturally occurring streams, they have several other applications, for instance: irrigation; reliable potable water for habitations; water transport without major loss from evaporation; avoidance of pollution in a water supply; and its protection during natural or military disasters. Types of qanat have been in use as far east as China and as far west as Chile and Peru. The oldest known such system has been functioning in what is now Iran for 2700 years and continues today to provide water for drinking and agriculture to a community of over 40,000. (Indeed, by some estimates, 80% of Iran's water supplies are still derived from qanats.)

Qanats used for cooling typically employ methods to draw room air over water in a qanat tunnel. The water is normally used for irrigation and drinking in addition to the temperature lowering applications.

More sophisticated qanat technology can be combined with wind towers and/or involve the creation of recyclable mists (in drier climes), to provide the greatest mercury lowering effects.

If the qanat and wind tower architectures are employed in conjunction with one another, the cooling results can seem amazing to anyone used to thinking of electrically powered AC systems as the only reasonable answer to summer heat. Temperature lowering of 20-30°F may be routinely measured, in summer and during the heat of the day outside, without supplementary cooling from an electrically operated air-conditioning system.

Nor are these principles applicable only for small abodes. Such systems have been put in place in larger buildings, including at California's Stanford University. The campus has pioneered the application of Middle Eastern mist and wind tower technology in some of its new construction and with excellent results. It reports that on hot days the temperature below the wind tower is about 25 degrees cooler than the outside temperature. They have not been able yet to do without traditional electrical AC systems, but the wind tower makes a significant contribution to lowering their costs and energy usage.

Elsewhere, as in Italy, large buildings have been constructed using more sophisticated but similar systems that capture and circulate the wind to augment electrically operated AC systems. In some cases, 75% of the energy use from a modern AC system may be eliminated without decreasing the comfort of building occupants.

In the future, as potable water becomes less abundant or sources less reliable and conventional air-conditioning too expensive, too harmful to the environment, or too inefficient to cope with advancing summer temperatures, a new contractor niche may appear: architectural entrepreneurs, like my brother Andy (though he would likely be retired by then), who offer to convert traditional AC cooled buildings, such as most of us came to accept as essential in the latter 20th Century, into truly efficient, self-cooling residences and office buildings that primarilly utilize, instead, the natural processes of wind and water.

Areas along the coasts (as with Stanford) or in flat, windy regions, such as in the American plains states, the southwestern US, much of Mexico, Africa, Australia, etc., would seem to be ideal for the use of these ancient remedies for too quickly rising mercury.

Within ten or twenty years, private equity may be pouring millions or even billions of dollars into new means to apply these ancient approaches to 21st Century building needs. In any case, the coming climate related design adjustments should help make architecture a quite interesting field over the next couple generations. It seems probable that such alterations may owe much to techniques developed long ago, under conditions not unlike those many may be facing as a result of global warming.

Passive Cooling Systems in Iranian Architecture. Arthur Bowen, et al, in Scientific American; Vol. 238, No. 2, pages 144-152, February, 1978.

Qanat. In Wikipedia.

Sahara Desert Born 4,000 Years Ago. David Whitehouse in BBC News; July 9, 1999.

Ancient Air-Conditioning. In BBC News - The World; January 11, 2007.

Recent Developments in Passive Downdraught Cooling - An Architectural Perspective. Elizabeth Francis and Brian Ford in European Directory of Sustainable and Energy Efficient Building - Yearbook; 1999.