Inflated ETFE Cushions on a Geodesic Dome
A Builder’s FAQ for a Container-Shipped Seastead

Fabrication, cost, material options, service life, and what happens to solar output when the panels live inside the skin instead of outside it.

Quick Answers

All three names you listed are legitimate. The industry term is an “ETFE cushion system” (Vector Foiltec’s brand name is Texlon®).
Cushions are factory-made, not site-made. You order them custom-welded to your dome’s exact geometry; on-site work is limited to clamping them into the frame and inflating them.
A geodesic layout is unusually friendly to custom fabrication, because a 3V–4V dome has only a handful of unique triangle shapes — you order multiples of each pattern.
Planning-level cost: roughly $25–$60/ft² for small-batch fabricated cushions, versus $12–$30/ft² at large-project pricing. Budget DIY alternatives exist.
Lifespan: 25–40 years is a realistic design life for the film; individual cushions are replaceable without touching their neighbors.
Solar under the skin: expect roughly 70–85% of a clean, ideally-placed exterior array — but close to parity (85–95%) with a real-world salt-sprayed exterior array that only gets washed occasionally.

1. Terminology — Are Those the Right Names?

Yes — all three phrases you used describe the same family of product, with slightly different emphasis:

Term	Where you’ll see it	Notes
ETFE cushion roof / facade	Architectural press, fabricator brochures	The standard industry term. ETFE = ethylene tetrafluoroethylene, a fluoropolymer film.
Pneumatic ETFE membrane cladding	Technical/engineering literature	Emphasizes that the cushions are kept rigid by internal air pressure (typically 200–800 Pa) and small automatic pumps.
Inflated foil cushions on a triangulated gridshell	Descriptive/design usage	One clarification: cushions need a framed edge to clamp to. A pure tension gridshell won’t work — but a geodesic dome’s compression struts are exactly the perimeter beams each cushion needs. So your instinct is structurally correct.
Texlon®	Vector Foiltec marketing	The original branded cushion system (Eden Project, Allianz Arena, Beijing Water Cube).

Cushion cross-section: two welded film layers, clamped by keder rope into aluminum extrusions along every dome strut, held taut by low-pressure air.

2. How Custom Cushions Are Made — Factory or On-Site?

Ordered custom-made, manufactured in a factory, assembled on site. Nobody pattern-cuts and welds architectural ETFE cushions in the field except for repairs. The workflow looks like this:

Step	Where	What happens
1. Geometry modeling	Engineer / fabricator	Your dome is modeled in 3D. Each triangle becomes a pillow spanning strut-to-strut; the frame carries wind and wave loads, the cushion carries only local air pressure.
2. Pattern flattening	Fabricator (specialized software)	The doubly-curved cushion shape is “unrolled” into 2D cutting patterns, compensating for film stretch and weld shrinkage.
3. CNC cutting	Factory	Film strips are cut from rolls (typically 1.5–2.5 m wide, 50–250 µm thick).
4. Welding	Factory	Strips are hot-wedge / high-frequency welded into full-size layers; layers are welded together at the perimeter; an inflation valve is added.
5. Pressure test & QC	Factory	Each cushion is inflated and leak-checked before shipping.
6. Packing	Factory	Cushions are folded flat into crates. This is the killer feature for your container goal — the entire skin of a 50-ft dome packs into a few pallets weighing a few hundred kg.
7. Installation	Site	Keder ropes slide into aluminum extrusion channels (or bolted clamp plates) along each strut; cushions inflate in minutes and self-tension.

Why a geodesic dome is the cheap way to buy custom cushions

A fully custom freeform facade might need every panel to be a unique pattern. A 3V–4V icosahedral dome works out to roughly 4 to a dozen distinct triangle geometries (exact count depends on subdivision frequency and truncation), and you order multiples of each.
Pattern-engineering fees are charged per unique shape, so repetition amortizes the setup cost dramatically.
Tolerances are forgiving: the keder/clamp connection allows adjustment, and slight oversizing is designed in.

DIY route (worth knowing about): ETFE film can be bought by the roll and welded with a temperature-controlled hot-air or hot-wedge welder (the same tools used for field repairs). Seams won’t match factory quality at first, but for prototype cushions this is how you could validate the concept for hundreds, not thousands, of dollars. Practice on scraps first — weld temperature control is everything.

3. What Do They Cost?

Honest answer: wildly variable, and small custom batches carry a big premium. Most famous fabricators (Vector Foiltec, Taiyo/MakMax, Birdair, FabriTec, Covertex, ExTech, Skypan) focus on large architectural contracts; for a one-off dome you’ll want smaller tensile-structure shops, which are more likely to quote a small job. Planning-level numbers:

Item	Planning range (USD)	Notes
Raw ETFE film (per layer, by the roll)	$2–$6 /ft²	Roughly 1–2 rolls cover one layer of a 50-ft dome’s skin.
Fabricated cushions, small custom batch	$25–$60 /ft²	Welded, valved, kedered, tested. Setup fees dominate at this scale.
Same cushions at large-project pricing	$12–$30 /ft²	What stadiums pay; useful as the long-term price ceiling.
Pattern engineering / NRE for a bespoke dome set	$5k–$25k one-time	Amortized across all cushions; low for geodesic because of repeated shapes.
Auto-pressurization kit (pumps, sensors, manifold)	$2k–$8k	Small, low-power, essential. Redundancy recommended at sea.
Complete engineered + installed envelope	$75–$150+ /ft²	Includes structure, cushions, controls, labor — the turnkey number.

Worked illustration: 50-ft diameter dome

Skin area (hemisphere to 3/4 sphere): roughly 1,500–2,200 ft²
Cushions alone, small-batch: ~$40k–$130k
Add frame (aluminum struts + hubs, marine-grade): often another $30k–$80k in material
Total skin + structure, self-built: very roughly $80k–$200k before fit-out
Shipping: the whole envelope — folded cushions, nested struts, hubs, pumps — fits comfortably in a fraction of one 40-ft container alongside interior equipment.

Budget alternatives

Alternative	Approx. cost	Trade-off
Single-layer tensioned ETFE (no cushion)	$8–$15 /ft²	No insulation, can flutter in wind, but same clarity and life.
Inflated polyethylene (PE) pillows, DIY-welded	$3–$8 /ft²	Same geometry concept, 3–7 year life, UV degrades it. Good prototype.
Translucent PVC-coated polyester cushions	$10–$20 /ft²	Cheaper and tougher to handle; yellows over 10–15 years, lower light.

Get three quotes. Send fabricators your dome geometry (even a SketchUp/Rhino model) and ask for supply-only cushion pricing separately from installation. Supply-only is the number that matters for a self-build seastead.

4. Clear, Opaque, Reflective, Insulative — Your Options

Each film layer is a separate choice, so a cushion is a “sandwich” you can spec per triangle or per zone. Key numbers:

Build-up	U-value (W/m²·K)	Visible light	Best use
Single layer	~5–6	92–95%	Mild climates, porches, budget builds
2-layer cushion	~2.8–3.0	~88–91%	Standard default
3-layer cushion	~1.8–2.2	~82–86%	Good insulation/light balance
4-layer cushion	~1.2–1.5	~75–82%	Cool nights, AC savings
5-layer + low-E coating	~0.9–1.2	~65–75%	Near-glazing insulation performance

Surface treatments available per layer

Option	Effect	Watch-outs
Clear	Maximum light; ETFE also passes most UV (glass doesn’t)	You can sunburn inside. For living space, specify a UV-absorbing film grade or coating.
Tinted (bronze, blue, green, gray)	Cuts glare and solar heat gain	Costs light; tint choice affects interior color cast.
Fritted / printed (white ink dots, any coverage %, gradients)	Tunable shading — the workhorse for comfort control	Printing is baked on at the factory; pick coverage per zone.
Low-E coated film	Reflects infrared back out; big U-value improvement	Slightly reduces light; adds cost per layer.
Opaque	Heavy print or opaque laminate; near-total block	Use for bedrooms, bathrooms, battery/equipment bays.
Reflective / metallized	Specialty films exist for high solar rejection	Rare, expensive, and usually unnecessary vs. frit + low-E combos.

A sensible zone strategy: clear apex feeding daylight and the interior PV plane, progressively more shaded and insulated toward the living spaces at the base.

5. How Long Do They Last?

ETFE is exceptionally UV-stable — it’s the same polymer family as Teflon and doesn’t meaningfully photo-degrade. Manufacturers commonly reference a 25–50 year potential life; material warranties typically run 10–15 years. Large installations from the 1980s–90s are still in service, and the Eden Project cushions (installed 2000–2001) remain original equipment.

Material	Typical service life	Primary failure mode	Marine suitability
ETFE cushion	25–40 yr	Puncture/tear (patchable), valve/pump wear	Excellent — salt inert, self-cleaning surface sheds spray residue
Single-layer ETFE	25–40 yr	Tear, flutter fatigue	Excellent
PTFE-glass fabric	25–40+ yr	Handling damage	Excellent but opaque-ish, heavy
PVC-coated polyester	10–20 yr	UV yellowing, plasticizer loss	Fair
Polycarbonate glazing	10–20 yr	UV yellowing, hazing	Fair
PE film	2–7 yr	UV breakdown	Poor (prototype only)

Replacement model — the good news

Cushions are individually replaceable: unclamp the keder rope, fold the old one out, slide a new one in, reinflate. Neighbors are untouched.
Field repairs are routine: ETFE repair tape for small punctures, hand hot-air welding for larger tears. Keep a patch kit and spare film aboard.
Because you’ll know your 4–12 unique triangle patterns, spares are cheap — order 2–3 spare cushions of each type with the original batch.

Suggested maintenance rhythm

Monthly: visual walk-around for tears, sagging (low pressure), dirty sensors.
Quarterly: verify plenum pressures; exercise backup pump.
Annually: fresh-water rinse of the skin (rain does most of the work — ETFE’s non-stick surface is famously self-cleaning); inspect clamp gaskets and fasteners (316 stainless).
As-needed: valve and pump replacement (cheap, off-the-shelf components).

6. Solar Panels Inside the Dome — How Much Power Do You Lose?

Short answer: a clean-sheet penalty of roughly 15–30%, but a real-world penalty of only 5–15% once you account for what salt spray does to exterior arrays. Here’s the loss ledger:

Factor	Typical effect	Notes
Transmission through the skin	−8% to −15%	Single clear film ~93–95%; a 3-layer cushion ~82–86%. ETFE’s transparency extends deep into the near-infrared where silicon panels produce, so spectral losses are minimal.
Curvature / oblique angles	−3% to −8%	Light striking the dome at grazing angles reflects off the film instead of entering. Worst for panels mounted low on the sides; negligible near the apex.
Greenhouse heating of panels	−3% to −10%	Cell output drops ~0.35–0.45%/°C above 25°C. Mitigate with ridge vents, a 50–100 mm air gap under the panels, and never bonding panels directly to the film.
Frame shading	−2% to −5%	Struts cast moving shadows; string-level optimization or micro-inverters help.
Gain: zero soiling	+5% to +15%	This is the sleeper advantage. Exterior marine panels develop a salt film that is sticky and surprisingly costly — 5–20% losses between washings are normal at sea. Interior panels stay factory-clean forever.
Gain: zero weather stress	Reliability, not %	No wind uplift, no hail, no salt corrosion of frames/connectors, no waterproofing failures. You can safely use cheap, fragile, lightweight glass-free modules outdoors-rated gear would reject.

Verdict: Compared to a hypothetical perfectly-clean, optimally-tilted exterior array, plan on 70–85% of output. Compared to a realistic exterior array on a boat or seastead — fixed mounting, salt film, occasional washing — the interior array lands at roughly 85–95% parity, with far better uptime and lifespan. The protection is usually worth more than the photons you give up.

Illustrative energy math (50-ft dome, trade-wind latitudes)

Usable interior panel area under the apex: ~90 m² (about 970 ft²)
Lightweight glass-free modules at ~19% efficiency: ~17 kWp
Ocean insolation ~5.5 peak-sun-hours/day: 17 kW × 5.5 h ≈ 94 kWh/day ideal
System derating (≈0.85) × dome factor (≈0.78): ~60–65 kWh/day

Illustration only — actual yield depends on latitude, season, panel layout, and ventilation.

Implementation tips

Mount panels on secondary purlins spanning between struts, with an air gap beneath — never adhesive-bonded to the film (heat + film creep will destroy both).
Flexible thin-film (CIGS) laminates are tempting for the curve, but they run hot and inefficient (~10–13%); lightweight glass-free mono modules (~3–5 kg/m², 18–21%) are usually the better trade.
Run wiring in conduit clipped along the struts — you get the protected, salt-free environment you wanted, for the wiring too.
Consider a hybrid: interior array as the protected workhorse, plus a small exterior wing on the base ring or a separate float canopy for redundancy and winter-angle capture.
A light-colored deck under the panels adds a small bifacial/albedo boost if you use bifacial modules.

7. Practical Notes for the Seastead Build

Container math works. Folded cushions: a few hundred kg on a few pallets. Aluminum struts nest in bundles; hubs are the bulkiest item. A 50-ft dome’s complete envelope leaves most of a 40-ft container free for interior fit-out, watermaker, batteries, etc.
The dome skin is not the hard part. Wind and wave loads on a 50-ft structure at sea are a serious naval-architecture problem — budget real engineering effort for the frame, hubs, and the hull/platform interface.
Condensation is your main comfort enemy. Warm humid air meets the cool inner film and drips. Insulated multi-layer cushions, a ventilated base ring, and drip-management detailing solve most of it.
Rain noise is real. Thin film drums loudly in a squall. Multi-layer cushions are quieter than single layer; an interior liner or ceiling fabric over living areas fixes the rest.
Specify UV-filtering film over occupied zones unless you want to tan indoors — standard ETFE passes the UV that glass blocks.
Order spares with the batch: 2–3 spare cushions per unique shape, spare valve stems, a pump, repair tape, and a hand welder. At sea, the spare you have is worth ten you’d order.