Our wise spokes owl answers frequent questions.
GardenDome Questions:
1. I heard that Buckminster Fuller didn't invent the geodesic dome. Some other guy did. Is that true?
Yes that is true, but Buckminster Fuller coined the name "geodesic dome", so he is the inventor of the name.
Walther Bauersfeld, the chief engineer of the Carl Zeiss Optical Company, designed the first “geodesic” dome after World War I for a planetarium to house his planetarium projector. The dome was patented, constructed by the firm of Dykerhoff and Wydmann on the roof of the Zeiss plant in Jena, Germany, and opened to the public in July 1926.
Buckminster Fuller coined the name “geodesic dome” from field experiments with artist Kenneth Snelson at Black Mountain College in 1948 and 1949. Snelson and Fuller worked developing what they termed "tensegrity," an engineering principle of continuous tension and discontinuous compression that allowed domes to deploy a lightweight lattice of interlocking icosahedrons that could be skinned with a protective cover. The “omnitriangulated" surface of geodesic domes provides inherently stable structures, the strongest structures for their weight ever devised. Although Fuller was not the original inventor, he developed the intrinsic mathematics of the geodesic dome and popularized application of the idea — for which he received U.S. patent 2,682,235 on June 29, 1954. Buckminster Fuller popularized the panelized (panel & frame) technique with the Sun Dome, a swimming pool cover published in the May 1966 issue of Popular Science. This technique was later adopted by many Geodesic Dome builders, and now of course by Optimum Wisdom Laboratories.
Walther Bauersfeld, the chief engineer of the Carl Zeiss Optical Company, designed the first “geodesic” dome after World War I for a planetarium to house his planetarium projector. The dome was patented, constructed by the firm of Dykerhoff and Wydmann on the roof of the Zeiss plant in Jena, Germany, and opened to the public in July 1926.
Buckminster Fuller coined the name “geodesic dome” from field experiments with artist Kenneth Snelson at Black Mountain College in 1948 and 1949. Snelson and Fuller worked developing what they termed "tensegrity," an engineering principle of continuous tension and discontinuous compression that allowed domes to deploy a lightweight lattice of interlocking icosahedrons that could be skinned with a protective cover. The “omnitriangulated" surface of geodesic domes provides inherently stable structures, the strongest structures for their weight ever devised. Although Fuller was not the original inventor, he developed the intrinsic mathematics of the geodesic dome and popularized application of the idea — for which he received U.S. patent 2,682,235 on June 29, 1954. Buckminster Fuller popularized the panelized (panel & frame) technique with the Sun Dome, a swimming pool cover published in the May 1966 issue of Popular Science. This technique was later adopted by many Geodesic Dome builders, and now of course by Optimum Wisdom Laboratories.
2. Could the geodesic dome built with these plans be turned into a small house?
No, the plans are optimized for low cost and simple construction using common woodworking tools and lumber.
GardenDome uses greenhouse 6 mil polyethylene film stretched over a wood strut framework and stapled to the edges. When assembled, the staples and raw polyethylene edges are hidden between the two panel edges. The greenhouse plastic is an insufficient cover for a house.
I personally discourage any one making a dome house because fixtures, furniture etc. expect rectangles for shapes. In addition, a geodesic dome is difficult to roof, drywall, trim, finish, plumb, wire or any other common building endeavor. Each triangle needs to be insulated and finished individually, both inside and out. GardenDome uses 99 equilateral triangles. Finding a roofer and a drywaller to finish your house with 99 triangles will be difficult, maybe impossible. Also, the triangles do not make efficient use of common rectangular shaped building materials that come in 4 foot x 8 or 12 foot sizes. Dealing with standard rectangular windows and doors is also problematic.
GardenDome uses greenhouse 6 mil polyethylene film stretched over a wood strut framework and stapled to the edges. When assembled, the staples and raw polyethylene edges are hidden between the two panel edges. The greenhouse plastic is an insufficient cover for a house.
I personally discourage any one making a dome house because fixtures, furniture etc. expect rectangles for shapes. In addition, a geodesic dome is difficult to roof, drywall, trim, finish, plumb, wire or any other common building endeavor. Each triangle needs to be insulated and finished individually, both inside and out. GardenDome uses 99 equilateral triangles. Finding a roofer and a drywaller to finish your house with 99 triangles will be difficult, maybe impossible. Also, the triangles do not make efficient use of common rectangular shaped building materials that come in 4 foot x 8 or 12 foot sizes. Dealing with standard rectangular windows and doors is also problematic.
Though not suitable for a home, the geodesic dome provides an ideal environment for a greenhouse, but a quite hostile one for anything rectangular. Standard rectangular raised beds are too inefficient. The 7 trapezoids and an octagon (shown below) provides an attractive walkway with minimal wasted space. Plants, as it turns out, don't require rectangles, and it allowed us to create more interesting raised bed frames.
3. Do the plans tell how to make a larger Dome?
Yes, but Dr. Petty optimized this plan for efficient use of standard 2x3 or 2x4 lumber and if followed you will create a 15.4-foot diameter dome. The builder is not required to do any math to build GardenDome, but Dr. Petty included all the formulas used to recalculate strut lengths in the plan if someone wants a different size.
An 18.6 diameter dome is 11.4 feet high (including base beams) with 240 square feet of floor area.
Dr. Petty built the GardenDome (with occasional help from his wife) and provides insight into what works and what does not. For example, the inexpensive automatic vent openers first used in GardenDome failed within one year and the 5 mm exterior plywood originally used in the door triangles was delaminated in two years. Dr. Petty revised the plans to solve these and other problems. If you use the information provided in the plan to make a larger or smaller dome, you must do your own math and some of the insight Dr. Petty shares in the plan may not apply.
The GardenDome plans Table of Contents will refer you to the design and calculation factors page.
Warning: Scaling this plan beyond 18.6 feet may provide insufficient support for both the wood framework and the greenhouse polyethylene film. An 18.6-foot dome can be reasonably built efficiently using standard 2x4x8 lumber.
Beyond 18.6 feet could require a different design (4V) that requires 6 different triangle types, 6 different templates, and likely more than just two people to assemble it. Dr. Petty does not intend to produce such a plan since it violates his "simple to build" principle.
- A builder in Canada used the formulas and the plans to build a dome 18.6 feet in diameter.
- In Indiana, a father and his grade seven son used the plans and the formulas to build a 10-foot diameter dome to house a small telescope in a backyard 'observatory'. For this awesome father-son project, the father conspired with his son's seventh-grade math teacher to get his son credit for doing the scaling math.
An 18.6 diameter dome is 11.4 feet high (including base beams) with 240 square feet of floor area.
Dr. Petty built the GardenDome (with occasional help from his wife) and provides insight into what works and what does not. For example, the inexpensive automatic vent openers first used in GardenDome failed within one year and the 5 mm exterior plywood originally used in the door triangles was delaminated in two years. Dr. Petty revised the plans to solve these and other problems. If you use the information provided in the plan to make a larger or smaller dome, you must do your own math and some of the insight Dr. Petty shares in the plan may not apply.
The GardenDome plans Table of Contents will refer you to the design and calculation factors page.
Warning: Scaling this plan beyond 18.6 feet may provide insufficient support for both the wood framework and the greenhouse polyethylene film. An 18.6-foot dome can be reasonably built efficiently using standard 2x4x8 lumber.
Beyond 18.6 feet could require a different design (4V) that requires 6 different triangle types, 6 different templates, and likely more than just two people to assemble it. Dr. Petty does not intend to produce such a plan since it violates his "simple to build" principle.
4. Can you briefly explain the science included in GardenDome that provides optimal conditions for plant growth?
The rate of photosynthesis (rate of plant growth) is controlled by three factors; light intensity, carbon-dioxide concentration, and temperature. At any given time, any one of these may become the limiting factor. The rate of photosynthesis is limited by the factor in shortest supply. Any change in the level of a limiting factor affects the rate of photosynthesis. As light intensity increases, the rate of photosynthesis increases proportionately until it is eventually limited by some other factor. Although the light dependent reactions of photosynthesis are not affected by changes in temperature, the light independent reactions of photosynthesis, reactions that are catalyzed by enzymes, are dependent on temperature. As the enzymes approach their optimum temperatures, the overall rate increases. The rate approximately doubles for every 10 degree C increase in temperature. Above the optimum temperature the rate decreases as enzymes denature, until it stops. A greenhouse doesn't control the carbon-dioxide concentration, but can impact both the temperature and the amount of light collected.
Every latitude on earth receives the same total hours of sunlight a year. The equator receives sunlight 12 hours each day all year. The higher latitudes receive more than 12 hours of sunlight each day between the vernal equinox and he autumnal equinox and less between the autumnal equinox and the vernal equinox. For example, at 48.3 degrees north latitude, at the summer Solstice we receive 16.1 hours of direct sunlight each day from 52 degrees northeast to 307 degrees northwest.
The GardenDome's hemi-spherical shape provides for optimal sunlight collection throughout the day through all seasons, providing both heat and light and the automatically controlled vents, as seen next photograph, keeps the temperature at or below the optimum.
This extends the average Northwest Montana 82 day growing season
(June 16 – September 6)
to 286 days
(March 6 – November 10).
Dr. Petty's wife, Ann, describes how GardenDome provides fresh produce during spring, summer, and fall plus some she cans or dries for winter in this YouTube video.
Every latitude on earth receives the same total hours of sunlight a year. The equator receives sunlight 12 hours each day all year. The higher latitudes receive more than 12 hours of sunlight each day between the vernal equinox and he autumnal equinox and less between the autumnal equinox and the vernal equinox. For example, at 48.3 degrees north latitude, at the summer Solstice we receive 16.1 hours of direct sunlight each day from 52 degrees northeast to 307 degrees northwest.
The GardenDome's hemi-spherical shape provides for optimal sunlight collection throughout the day through all seasons, providing both heat and light and the automatically controlled vents, as seen next photograph, keeps the temperature at or below the optimum.
This extends the average Northwest Montana 82 day growing season
(June 16 – September 6)
to 286 days
(March 6 – November 10).
Dr. Petty's wife, Ann, describes how GardenDome provides fresh produce during spring, summer, and fall plus some she cans or dries for winter in this YouTube video.
5. Does GardenDome use a double layer of poly for improved performance in the winter.
No. GardenDome uses a single layer of greenhouse polyethylene that feature UVA and dust protection, IR reflectors, Anti-Drip (AD) and mold inhibitors. Polyethylene films available at big box stores like Home Depot or Lowe's contain no UV inhibitors and will degrade in the direct sun within a year. The IR (infra-red) reflector minimizes radiant losses.
The heat loss from any building is due to:
GardenDome reduces conduction losses by reducing the conductive surface area. A sphere has the lowest surface to volume ratio of any structure, and the hemispherical shape of a dome provides the minimum conductive surface area for a given volume. A double layer would reduce the convective losses, but not the primary (radiant) heat loss.
Except for the door and the vents, GardenDome is sealed, minimizing the third factor in heat loss.
Finally, GardenDome is not designed for greenhouse use in winter snow. It withstands the snow load as shown in the next photograph, but would require us to maintain a 148 foot (45 meter) long path from our house through 40 inch (1000 mm) deep snow to visit. GardenDome provides little practical greenhouse use beyond the extended growing season described in question 4 above. However, Dr. Petty's wife discovered a late fall planting of spinach thriving the following spring.
5. Does GardenDome use a double layer of poly for improved performance in the winter.
No. GardenDome uses a single layer of greenhouse polyethylene that feature UVA and dust protection, IR reflectors, Anti-Drip (AD) and mold inhibitors. Polyethylene films available at big box stores like Home Depot or Lowe's contain no UV inhibitors and will degrade in the direct sun within a year. The IR (infra-red) reflector minimizes radiant losses.
The heat loss from any building is due to:
- radiation
- conduction of heat through walls, windows and doors
- leakage of warm air around doors, windows and through the walls themselves.
GardenDome reduces conduction losses by reducing the conductive surface area. A sphere has the lowest surface to volume ratio of any structure, and the hemispherical shape of a dome provides the minimum conductive surface area for a given volume. A double layer would reduce the convective losses, but not the primary (radiant) heat loss.
Except for the door and the vents, GardenDome is sealed, minimizing the third factor in heat loss.
Finally, GardenDome is not designed for greenhouse use in winter snow. It withstands the snow load as shown in the next photograph, but would require us to maintain a 148 foot (45 meter) long path from our house through 40 inch (1000 mm) deep snow to visit. GardenDome provides little practical greenhouse use beyond the extended growing season described in question 4 above. However, Dr. Petty's wife discovered a late fall planting of spinach thriving the following spring.
6. Did you consider alternative Geodesic Dome construction techniques?
I considered only techniques that required no industrial fabrication or professional fabrication equipment like, welders, milling machines, CNC cutting equipment and heavy-duty saws.
Alternative techniques include:
I considered only techniques that required no industrial fabrication or professional fabrication equipment like, welders, milling machines, CNC cutting equipment and heavy-duty saws.
Alternative techniques include:
- Flattened Conduit is one of the simplest ways to build a geodesic dome frame. Simply flatten both ends of metal tubing (conduit), bend the ends slightly, then drill holes. Connect the flattened conduit struts with bolts, washers, and nuts to form the required dome.
Conduit Domes are easily assembled/disassembled and often used for portable or temporary enclosures. Because joints don't finish level, they can only be covered with flexible material.
- Classic Wood Strut systems are beautiful, but require 2 complex dual beveled compound miter cuts at each strut end. The precision tenth-degree angles required are neither simple nor even possible using commonly available woodworking tools and skills
- Reinforced Classic Wood Strut. Some manufactures use the classic dual-beveled wood struts because of their inherent beauty, but then reinforce the joint, possibly to compensate for their inherent weakness.
The possibility of an inherent weakness adds to the justification for using an alternative to the Classic Wood Strut system for The Dome.
- Hubs simplify construction by providing the complex dual bevel angles, just cut the beams to the correct length.
However, Hubs are expensive. To construct GardenDome using hubs would require:
40 – 6 way connectors
6 – 5 way connectors
15 – 4 way connectors
and would cost over $700 just for the hubs.
- Hubless Panelized Timber Frames (Good Karma Domes for example and pictures) use separately framed timbers covered in plywood. The three members comprising the triangular frame are cut at one half the dihedral angle ( angle between two intersecting planes) to provide for a flat fitting of the various triangles. Holes are drilled through the members at precise locations, and steel bolts then connect the triangles to form the dome. The panelized technique allows the builder to attach the plywood skin to the triangles while safely working on the ground or in a comfortable shop out of the weather. Buckminster Fuller popularized this technique with the Sun Dome, a swimming pool cover published in the May 1966 issue of Popular Science.
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