TENSEGRITY CLIMATE ENVELOPE

An architecture with trees, arbors, and flowers for interior partitions and decorations, with the outdoor landscape invading rooms while leaving bad weather outside, is made possible and comfortable with Low-Emissivity and Cloud Gel.  The Climate Envelope will transform architecture in a way architects can’t; molecular design trumps design with mere visible objects.  Pockets of tropical weather will make the world a friendlier place for the northern populations whose industry is killing the planet.  Banana trees with ripe fruit in the dead of winter will make us feel safe enough to open our eyes and hearts to the miracle of life.  And stop killing the plants and animals that our lives depend on.

For large span Climate Envelopes, two economical structural systems are presented here: the Tensile Flexahedron (see next section), and the Tensegrity, which offers:

Snow removal and low heat loss become important for avoiding supplemental heating in climates north of Washington, D.C., for example.

Bucky Fuller said that after designing a building, one should weigh it, taking a page from the airplane designer’s book (“simplicate and add lightness”), while speaking to a future generation’s awareness of environmental impact. The Tensegrity Climate Envelope takes the prize with its low building and operating costs, large span, automated production, and easy field assembly.  Except for a few struts, masts, and anchors, every line and surface of this envelope geometry is under tension, and therefore light and cheap.  Thus reducing building costs almost to that of a sheet metal warehouse and minimizing the environmental costs of manufacturing and recycling building materials. While nearly eliminating the building’s operating costs and pollution with Low-Emissivity and Cloud Gel. 

What have we here, covering many acres?  Concrete for mast pads and anchor pilings, steel pipe for struts and masts, steel cables, a plastic like Teflon for the transparent skin, and, of course, Low-Emissivity and Cloud Gel. That’s it. From inside, the envelope will be practically invisible; just a far away transparent or translucent roof, some small, widely spaced pipes and cables, and very few large masts.

Shown below is a large Tensegrity Envelope sheltering its tropical climate from the ravages of a northern winter. This drawing was originally for an expensive glass and steel girder Envelope, but the inexpensive Tensegrity Envelope with a 50-year plastic glazing would look the same.

Finished Tensegrity Supported Building

In Figure 1, the Tensegrity structural system makes the simplest shape Envelope:  2 masts support 5 tensegrity beams, between which are stretched 4 tensegrity space grids.  The beams tension the space grids, and transfer their loads to the masts and ground anchors.  For clarity, only the bottom lattice of the space grids is shown.  This lattice is infilled with the transparent weather skin, which is the outer surface of the Envelope.  For the vertical exterior walls, the weather skin separates from the space lattice and drops to its small foundation anchors.

The transparent plastic film from which the weather skin panels are made is ETFE, a relative of Teflon with the same durability, lasting for 50 years in sunlight and weather; the same low friction, so snow will slide off and dust won’t stick and block sunlight; almost the same non-flammability; and the same high price, about $5 per square foot ($60 per square meter).  ETFE has a much higher sunlight transmission than glass, especially after a few years of weathering; and you would break a pencil trying to poke through it.

Tensegrity Climactic Envelope

Figure 1: simple tensegrity structure

Figure 2 is a cross section of the Envelope, showing 2 Tensegrity space grids from the edge.  They are stretched between ground anchors and the ridge beam.  Enclosing the living space are Climate Panels that are made from Low‑Emissivity and Cloud Gel, and which transform winter climates into tropical.  These panels are suspended with wires from the space grids to form the ceiling, and are attached to the weather skins for the walls.  Hanging the panels below the Weather skins reduces their surface area, thus greatly reducing heat loss and cost, and slightly increasing light transmission.  The living space enclosure is transparent when it is below 75°F, and white above 75° (24°C).  Except the vertical walls remain clear.

Figure 2: vault cross-section

Figure 3 shows the Tensegrity Space Grid.  The pairs of black load bearing cables stretch between the tensegrity beams on one end, and ground anchors on the other.  Together with the short pipes, the load bearing cables under tension behave structurally like the rafters in an A-frame building.  The red and blue stabilizing cables are structurally like an A-frame’s plywood cladding.

Figure 3: tensegrity grid

The steel hub that connects the various cables and the pipe struts is shown in Figure 4.  Its minimal cost derives from its simplicity.  The thee dimensional cable network is woven like cloth from long cables, rather than joining many short pieces of cable at hub.  Its factory assembly is simply tightening the hub bolts.  The resulting cable network is flexible and may be bundled together for shipping.  The pipe struts are put into the hub sockets on site.

Tensegrity Hub

Figure 4: tensegrity grid hub

The weather skins and Climate Panels are installed with plastic zippers, as shown in Figure 5.  The zippers are extruded from a transparent fluropolymer, such as PVDF with a bit of PVDF/HFP copolymer added for flexibility and clarity.  They are ultrasonically welded along the edges of the weather skins. The rectangular cable frames that the weather skin panels zip into have thin cables on two sides, and thick cables on the other two sides, as shown in Figure 3.  Drawings 1 to 3 of Figure 5 show how the zip attaches to a thin cable.

Drawing 4 shows how the zip attaches to its neighboring panel, which is on the other side of the cable.  The panels are a few percent undersized, so they must be stretched to zip to their neighbors.  This keeps the weather skin under tension.  The zipper (not shown) has thin wheels with a groove that fits the zip’s flange on the left of the cable, and similar wheels for the flange on the neighboring panel on the right of the cable.  The zipper wheels are powered by a small electric motor to stretch the weather skins while zipping them together.

Drawings 5 and 6 of Figure 5 show the same procedure for fastening the weather skin panels to the thick cables.  

Tensegrity Zippers

Figure 5: plastic zippers

Erection Procedure: The cement ground anchors for the load bearing cables, the small foundation anchors, and the mast pads are poured and cured.  The mast sections are assembled on site and erected.  The sections of cable network and the tensegrity beams are unfolded, bolted together, and bolted to their ground anchors.  The pipes, typically 5 feet (2 meters) long, are bolted into the cable network and beams.  The assembled but flexible space grids and beams are hauled up to the masts and bolted on.  At the ground anchors, the cables are tensioned, making all of the cable networks rigid and structural. 

The weather skin panels, typically 10 by 10 feet (3 by 3 meters), are zipped in from a cherry picker. Then the Climate Panels are zipped in.  The amount of labor is comparable to that for erecting a sheet metal warehouse, the cheapest building envelope.  Just as the Tensegrity Climate Envelope is zipped together, so it can be unzipped, shipped, and reassembled elsewhere; everything but the cement can be reused.  For temporary shelters, portable mast pads and anchors can be made of steel.

The Tensegrity Climate Envelope is a transparent, snow shedding weather shield made with Low-Emissivity and Cloud Gel that encloses a living space with the minimum materials.  Manufacturing and erection labor are minimal, with automated prefabrication of Climate Panels, and weather skin panels.  Thus the cost of the Tensegrity Climate Envelope is minimalized, while it maintains a tropical climate without supplemental heat as far north as the Canadian border.