Built to Last
Aside from being energy-efficient, geodesic domes homes are built to last. They are incredibly strong structures designed to withstand earthquakes, tornadoes and hurricanes. In fact, American Ingenuity (AI), a geodesic dome home manufacturer, says that during the 2004 Hurricane system, Florida experienced four hurricanes and not one of them damaged any of the homes they built in Florida, even though some were in the direct path of Charley, Ivan, Frances and Jeanne.
Geodesic Pay-offs
People who own geodesic homes can save anywhere from 50 to 70 percent on heating and air-conditioning costs over the conventional home owner because geodesic homes have one-third less surface area than traditional homes, have better insulation than traditional homes and are more air-tight than traditional homes. Also, there is an efficient airflow inside the dome because the curved walls help the air to circulate. For these reasons a geodesic dome can be heated by a single propane fueled gas log fire.
The Development of Domes
Dome-like living structures can be traced back to the days of the Romans and the domed huts of ancient Tunisians. Eskimo igloos, the spherical yurts of nomadic Mongols, and certain domed tepees of American Indians are all predecessors of the geodesic dome.
Modern domes have been built primarily according to designs by Buckminster Fuller, who conceived of constructing domes as a network of intersecting triangles, the triangle being the strongest geometric shape. One of Fuller's first domehome designs called for a home supported by a pole, with space below for a car and a jet-propelled, wingless aircraft. Called the "4-D House" (referring to Einstein's fourth dimension, time), the name was later changed to "The Dymaxion Dwelling Machine." Fuller later developed a future vision of cities covered by geodesic domes, with sunlight and weather easily regulated.
Today's geodesic dome is more likely to be three-eighths or five-eighths of a full sphere of intersecting triangular sections assembled on a conventional foundation. The triangular network design provides for a free-standing, self-supporting structure requiring no internal supports or load-bearing walls, thus opening up the interior of the dome for maximum space and light.
Due to the mathematics involved, the bigger the dome, the more energy efficient and materials efficient it becomes. The volume grows by a factor of eight every time the diameter is doubled, and the surface area increases by a factor of four.
Saturday, August 1, 2009
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 forty 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 eves 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.
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 eves 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.
Geodesic Domes History
Since the beginning, mankind's ambition has been to feed, protect and improve itself. 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. Dr. Walter Bauersfeld, using spherical geometry, was first to combine the strongest geometric shape, the triangle, with the sturdy arch in Jena, East Germany in 1922.
Some popular geodesic domes known today are:
- 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
- Biosphere desert project in Arizona
- 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
Monday, July 27, 2009
Geodesic dome - Lets Start Here...
A geodesic dome is a spherical or partial-spherical shell structure or lattice shell based on a network of great circles (geodesics) lying on the surface of a sphere. The geodesics intersect to form triangular elements that have local triangular rigidity and also distribute the stress across the entire structure. When completed to form a full sphere, it is known as a geodesic sphere.
Typically the design of a geodesic dome begins with an icosahedron inscribed in a sphere, tiling each triangular face with smaller triangles, then projecting the vertices of each tile to the sphere. The endpoints of the links of the completed sphere would then be the projected endpoints on the sphere's surface. If this is done exactly, each of the edges of the sub-triangles is slightly different lengths, so it would require a very large number of links of different sizes. To minimize the number of different sizes of links, various simplifications are made. The result is a compromise consisting of a pattern of triangles with their vertices lying approximately on the surface of the sphere. The edges of the triangles form approximate geodesic paths over the surface of the dome that distribute its weight.
Geodesic designs can be used to form any curved, enclosed space. Oddly-shaped designs would require calculating for and custom building of each individual strut, vertex or panel-resulting in potentially expensive construction. Because of the expense and complexity of design and fabrication of any geodesic dome, builders have tended to standardize on a few basic designs.
Typically the design of a geodesic dome begins with an icosahedron inscribed in a sphere, tiling each triangular face with smaller triangles, then projecting the vertices of each tile to the sphere. The endpoints of the links of the completed sphere would then be the projected endpoints on the sphere's surface. If this is done exactly, each of the edges of the sub-triangles is slightly different lengths, so it would require a very large number of links of different sizes. To minimize the number of different sizes of links, various simplifications are made. The result is a compromise consisting of a pattern of triangles with their vertices lying approximately on the surface of the sphere. The edges of the triangles form approximate geodesic paths over the surface of the dome that distribute its weight.
Geodesic designs can be used to form any curved, enclosed space. Oddly-shaped designs would require calculating for and custom building of each individual strut, vertex or panel-resulting in potentially expensive construction. Because of the expense and complexity of design and fabrication of any geodesic dome, builders have tended to standardize on a few basic designs.
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