A compact-shipping envelope for a seastead: triangulated frame + pneumatic foil pillows that pack into a 40-foot container and assemble into a large, weather-tight living volume.
All three names you listed are used in industry:
The usual construction is a lightweight metal strut-and-hub geodesic (or gridshell) with each triangular bay closed by a 2- to 5-layer ETFE “pillow” held at low positive pressure (typically 200–800 Pa). The pillows are the weather skin, the primary light source, and part of the thermal envelope.
They are almost always factory-fabricated, not built on site.
On-site welding of ETFE is possible but uncommon for a one-off seastead: quality control, clean-room conditions, and certified weld procedures are hard to reproduce on a barge or remote site. Order them made to the final surveyed geometry (or to the theoretical geometry plus a small tolerance). Specialist firms include Vector Foiltec, Taiyo / Birdair, Hightex, and several European and Asian membrane fabricators that already do geodesic and free-form ETFE work.
This is a premium architectural system, not a commodity greenhouse film.
Obtain a budget quote from two fabricators once you have a frequency, diameter, and layer count. Prices move with foil thickness, number of layers, print coverage, and how many unique panels you have.
| Property | How it is achieved |
|---|---|
| Clear / high light | Unprinted ETFE, 1–3 layers. Single-layer visible transmittance typically 94–97 %. Three-layer cushions still pass ~85–92 % depending on foil and angle. |
| Solar / glare control | Silver or white frit (dot or geometric print) on one or more layers, 20–70 % coverage. Variable-tint or electrochromic interlayers exist but add cost and complexity. |
| Opaque / private | Heavy white or colored print, or an opaque inner layer. Living zones can mix clear upper triangles with printed or opaque lower ones. |
| Reflective | Metallic or high-IR-reflectance prints; limited true mirror finishes. More common is selective low-e or solar-control print. |
| Insulative | More air layers. 2-layer is modest; 3–5 layers plus optional intermediate foils give U-values competitive with good double or triple glazing. Continuous low-pressure air is the insulator. Night-sky radiation can be reduced with low-e coatings or prints. |
ETFE itself is UV-stable, chemically inert (excellent in salt air), non-stick (self-cleaning in rain), and remains flexible at low temperatures. It transmits more UV than glass, which can be an advantage or a reason to add a UV-blocking print or inner layer if occupants or interiors need protection.
The foil is routinely warrantied 25–30 years and has demonstrated 40–50+ year durability on landmark buildings (Eden Project, Allianz Arena, etc.) with little yellowing or embrittlement. Failure modes are mechanical (puncture, clamp damage, storm-driven debris) or system-level (fan failure, neglected pressure). Individual cushions can be replaced without dismantling the whole dome; many owners plan a mid-life inspection and selective re-skin at 20–30 years rather than a calendar replacement of everything. Inflation blowers and sensors are consumables (years, not decades) and should be specified with marine-grade redundancy and easy swap-out.
For a seastead, budget periodic inspection of welds, clamps, and the air system, plus a small stock of repair tape and one or two spare cushions of the most common sizes.
A 50-foot (15.2 m) diameter dome used as a hemisphere or 5/8-sphere gives a useful floor on the order of 1,900+ sq ft plus possible loft volume, while the entire kit (struts, hubs, folded cushions, inflation gear, and a modest interior) can be designed to fit a single 40-foot container if the structure is aluminum and the cushions are packed efficiently.
Placing lightweight flexible modules on an internal rack or tensile net above the living zone, still inside the ETFE, trades some photons for a much kinder environment (no salt spray, no wind load, no hail, easier cleaning, simpler wiring).
Rough optical budget (clear, lightly fritted or unprinted 2- or 3-layer cushions):
Net result: the array will usually see about 75–88 % of the irradiance it would see on an unobstructed external mount of the same orientation. A planning figure of 15–25 % less energy is realistic for a well-designed clear cushion dome; the lower end if you keep prints minimal and the structure slender, the higher end if you add solar-control frit or extra layers for insulation.
Offsetting factors that often make the internal array still attractive on a seastead:
If maximum annual kWh is the only goal, a few external marine-rated modules on the float or on a small mast will outperform the internal array per watt installed. The internal array’s value is reliability and survivability. Hybrid (some external, bulk internal) is a common compromise.
Struts nest or bundle; hubs are small; cushions fold into a fraction of their inflated volume. A carefully nested 50-foot-class aluminum geodesic plus ETFE package, inflation plant, and a lightweight interior fit-out is a plausible single-40-foot-container payload. On-site (or on-deck) work is then: assemble the frame (a few days with a small crew and a gin pole or crane), clip cushions, inflate, weather-seal the base, and fit out. That is the core reason the typology matches a “ship small, live large” seastead brief.