By Chip Sullivan
For most parts of the country, the Hot August Nights are here. Current climate events, including excessive heat warnings and extreme weather patterns, reinforce the need for cooling landscape designs. There are numerous examples of historical landscape elements that employ passive design to moderate microclimates throughout the seasons. These historical techniques and practices illustrate a deep and intuitive understanding of the forces and processes of nature, from which contemporary designers would benefit.
The purposeful manipulation of garden elements can easily create microclimates that take advantage of the cooling properties of air flow and the high thermal mass of the Earth. While earth itself is not an insulating material, earthen structures do not transfer heat but absorb it, creating cool ambient temperatures. Throughout time, garden designers have sculpted the movement of air and designed air-cooled spaces in a variety of ways to exploit their cooling effects. Adapting these techniques today can reduce our dependence on energy consumptive mechanical air-conditioning.
The Venturi Effect describes how when air is forced through a small opening its velocity increases as it exits the opposite side of the opening. Many historical garden features take advantage of this effect. Air can be directed, funneled, and accelerated with simple landscape features such as seats, allées, arbors, garden pavilions, and porches. Adjustable fabric awnings and screens on the exterior of structures funnel the breezes, shade the interior, and provide a psychologically cooling effect from hearing and seeing the movement of the cloth. Subterranean vaulted corridors like the Roman cryptoporticus served a variety of structural and climate purposes. Integrating passive design elements into contemporary landscapes can reduce energy consumption and help lessen the detrimental effects of changing climates.
Here is an abbreviated chronology of some historical cooling landscape elements:
The sunken corridors, or cryptoportici, at Hadrian’s Villa in Tivoli, Italy (2nd cent.), directed cool air into the rooms above through openings in their arched ceilings (see image above). The passageways could also be inhabited during hot summer months.
Located at the edge of the pond, and facing a wall with latticework apertures, garden seats with open backs capture cool air passing above the water within the Garden of the Master of the Fishing Nets (12th cent.), in Suzhou, China.
At the Alcazar in Seville, Spain (13th cent.), an extremely thick wall with small openings contains a window seat facing the prevailing winds and views of the garden.
Hadrian’s precedent was adapted at nearby Villa d’Este (16th cent.), where air cooling cryptoportici were built into the steep hill forming the foundations of the villa. Small openings on the windward side catch the breezes and force the air over a series of cooling fountains before passing through vents to cool the rooms above.
Persian garden pavilions (c. 17th cent.) with fabric awnings attached to south-facing porches could be adjusted to accommodate changing weather conditions. Drawn out over the pool, they acted as air scoops to catch the cool air above the surface of the water, and provided additional shade.
Structure and site work in tandem at Divan Khanah, an 18th century dwelling in Shiraz, Iran. The solid northern wall of the residence blocks winter winds. The one-room-deep building contains an elevated porch open to the southern breezes. And the roof height produces shade in summer and allows the lower angle of the winter sun to penetrate the interior spaces.
The garden walls have small openings along the south, channeling the prevailing summer breezes into the garden. The air is cooled and the dust is filtered out by exterior trees and vegetation. A basin and water jet directly in front of the dwelling adds moisture to the air entering the structure.
The thick earthen walls of the garden grotto at Villa Vizcaya, in Miami, Florida (1914-23), drip with water which splashes on the ground and keeps the space cool in the hot summer.
La Posada Hotel, in Winslow, Arizona (1930), designed by architect Mary Colter, incorporates an astonishing number of historical climate design elements adapted to 20th century lifestyles. Passengers who traveled at that time by train through the parched desert landscape were welcomed into a green oasis with a well. A grove of trees protects the complex from the western sun. Loggias, which are rooms with one or more open sides, and citrus orchards located throughout the property provide comfortable spaces to sit. A sunken garden offers comfort and protection from ferocious dust storms.
Sited above a natural spring and oasis, Scotty’s Castle in Death Valley, California (1922-31), represents another use of historical “green” technology. The structure faces south; the hills to the north block the northern winds. A central courtyard creates a solar pocket and contributes to positive air circulation.
A cryptoporticus directs the air over the spring with powerful fans at the opening to increase air flow into the structure. Water-soaked burlap fabric was draped over the opening to further cool the air. A large air-cooling pool located in front of the structure is similar to those at historical Persian garden pavilions. In addition, the ranch maintained one of the earliest solar-powered water heaters, still in existence today. Power was generated by a Pelton wheel with banks of batteries to store the electricity.
Designers and builders of the past were ingenious at understanding and using the elements of nature to modify the climate, soothe the spirit, and delight the eye. Their techniques can serve as inspiration for a new order of sustainable climate design, grounded in practical and innovative interpretations of historical methods.
Chip Sullivan, FASLA, is Professor Emeritus of Landscape Architecture & Environmental Planning, College of Environmental Design, University of California at Berkeley. He is co-author of Wisdom of Place: A Guide to Recovering the Sacred Origins of Landscape (with Elizabeth Boults) and author of Field Sketching for Environmental Designers.