Terminology
A geodesic dome is a structure composed of a number of triangular facets, arranged in such a way as to approximate the surface of (a portion of) a sphere.
The term geodesic comes from the Greek geo (earth) + daiesthai (to divide); thus we have “earth dividing” domes. A geodesic line connecting two points on a given surface is the shortest curve that connects them and is entirely contained on that surface. So if we use geodesic lines to connect the vertices of the triangles that form a geodesic sphere, we end up forming great circles that divide the sphere.
History
Domes first appeared on round huts and tombs in the ancient Middle East, India and the Mediterranean in forms, such as solid mounds, adaptable only to the smallest buildings. The oldest civilizations evolved living in round yurts, igloos and teepees because of a need for strong shelter, the scarcity of building materials, and light weight that took the least effort to transport during migration.
Many of the world’s oldest and architecturally beautiful buildings in Europe and Asia are arched domes, or buildings with clear-span arch entries and halls built strong enough to survive the centuries. The Romans introduced the large-scale masonry hemisphere (such as the Pantheon). It was the Romans who first used geometric framing to build concrete domes, introducing the dome as a common architectural element which has survived in modern forms today.
Byzantine architects invented a technique for raising domes on piers, making the transition from a cubic base to the hemisphere by four pendentives. Bulbous or pointed domes were widely used in Islamic architecture. The design spread to Russia, where it gained great popularity in the form of the onion dome, a pointed, domelike roof structure.
The first contemporary geodesic dome on record is the German scientist/engineer Walter Bauersfeld’s, who realized the utility of projecting the constellations on the inner surface of an icosasphere, Omnimax-style, thereby designing a breakthrough planetarium, created by Zeiss Optical Works, in Jena, Germany, in 1922.
R. Buckminster Fuller is often credited with “inventing” the geodesic dome in the 1940s. In fact, by adopting the Greeks’ icosohedron, Fuller did develop and popularize the geodesic dome, and registerd his 1954 patent more than 30 years after Bauersfeld.
Fuller derived his dome from general principles independently of Bauresfeld, just as he derived the octet truss without knowing of Alexander Graham Bell’s implementation of this same naturally-occuring phenomenon.
Recent discoveries of complex, but highly stable, polyhedral molecules have been called Buckminster-Fullerines and Bucky-balls in his honor.
Some popular geodesic domes known today are:
- The Biosphere 2 desert project in Arizona (above)
- Future World Exhibition at Epcot Center in Walt Disney World
- Tacoma Dome in Washington State. At 530' in diameter, it is the largest public geodesic dome covering a football field and stands
- Minneapolis Convention Center, expanding to 500,000 sq. ft. under four low-profile domes
- America’s exhibit at the 1967 World Fair in Montreal, for which the United States commissioned Buckminster Fuller
- Milwaukee’s Mitchell Park Conservatory, with three geodesic domes sitting on elliptical bases that provide tropical flower gardens year round
- Des Moines Arboretum, a self-contained ecosphere
- Los Angeles city housing project with over two dozen domes
- Geodesic jungle gyms in many American city parks
- Thousands of family residences and cabins throughout North America, including the Dome Home in Big Bear
Geodesic Dome Facts
A sphere is defined as the geometric shape that encloses the most volume with the least surface area. A dome is the safest, strongest and most energy-efficient building. It takes less building materials to enclose usable living or working area in a dome than any other shaped structure. Forty feet of wall will enclose a 10 x 10 area, measuring 100 sq. ft., while 40 feet of wall built in a circle will enclose 127 sq. ft.—a 27% increase.
Geodesic domes offer the safest shelter in the most violent weather extremes around the world. In tornadoes and hurricanes, high winds and negative air pressure combine and get under the eaves and soffits of conventional housing, then rip the roof off, leaving the occupants exposed. A geodesic dome’s aerodynamic shape offers the best above-ground protection against winds from any direction, allowing gale-force winds to slip past. During an earthquake, a conventional house rocks off its foundation and topples as the earth makes lateral shifts. A dome has an even distribution of weight and a low center of gravity, so it moves with the earth. Engineering for incredible snow loads is intrinsic in its design. Insulating efficiently against extreme heat or cold is a direct factor of the exposed surface area, or outside wall area of any building. The vaulted ceiling in its free span interior allows excellent air circulation and heat recovery. You may design geodesic dome walls where you want them, if you want them, as you are unrestricted by bearing walls necessary to hold up a standard roof. There are no limits to interior design creativity.
The key structural unit in a geodesic dome is a four-surfaced pyramid figure called a tetrahedron. The geometric shape on which all geodesic domes are based is a 20-sided polyhedron called an icosahedron. Like the tetrahedron, each side is an equilateral triangle, and at each point five triangles meet to form pentagons. Unless it is a complete sphere, all geodesic domes have six pentagons—one at the top and five around the perimeter. The largest domes, hundreds of feet in diameter, have thousands of hexagons but still only six pentagons.
There are three ways to identify a geodesic dome: diameter, frequency and profile. The diameter is the distance from one side of the sphere to the other through the center point. The frequency is the number of framing members, called chords, from the center of any pentagon to the center of any other pentagon.
Typically, a dome building is flat on the bottom so it will sit flat on the ground, and the profile is a percentage of sphere, expressed as a fraction. An example: The Imagination Room geodesic dome displayed at the Science Museum of Minnesota is a three-frequency, 36' diameter, 4/9ths sphere.