1. What to call this system
All three of your terms are used and understood; each emphasizes something different:
- ETFE cushion roof / facade — the most common industry phrase. Individual panels are called cushions or pillows; a full assembly is an ETFE cushion system.
- Pneumatic ETFE membrane cladding — correct; emphasizes that panels are air-inflated (typically 200–300 Pa, roughly 0.03–0.04 psi).
- Inflated foil cushions on a triangulated gridshell — the most technically precise description of your concept, since a geodesic dome is a triangulated gridshell.
Useful vocabulary: the best-known brand system is Texlon® ETFE (Vector Foiltec). Film layers are typically 100–250 μm thick; cushions are 2–5 layers with 1–4 air chambers. Reference projects: Eden Project (2001), Beijing "Water Cube" (2008), Allianz Arena (2005), Khan Shatyr (2010).
2. How custom triangular cushions are made
Yes, they are custom — but only a few unique sizes. A 2V dome has 2 unique strut lengths and 2 unique triangle shapes; a 3V dome has 3 unique triangles. So "75 custom panels" is really "3 designs × 25 copies," which helps tooling and price enormously.
Standard route: fabricated off-site by a specialist
- You supply geometry: node coordinates (3D model or DXF), strut profiles, desired layer count, frit density, and where inflation feed points go.
- Patterning: the fabricator flattens each triangle into 2D cutting patterns with compensation added so the cushion bulges to a calculated camber (typically 10–15% of the shorter span) when inflated.
- Film & welding: ETFE comes in rolls ~1.5 m wide, so each face is assembled from strips joined by ~10–15 mm heat/impulse welds. Layers are welded together at the perimeter, and a keder (bulb rope) edge or clamp pocket is welded in.
- Frames: each cushion gets an extruded aluminum perimeter profile with EPDM gaskets that clamps into rails — in your case the dome's struts become the clamping rails.
- QC: each cushion is pressure/leak tested, labeled, then folded or rolled for shipping (ETFE tolerates folding; creases relax in the sun).
- Inflation: a small continuously-running blower unit with air dryer, filters, pressure sensors, and backup blower feeds all cushions through thin tubing. Pressure rises automatically (to ~700–800 Pa) in high wind. Greenhouse "double-poly" inflation fans are the low-cost cousin of this tech.
On-site fabrication?
Not realistic for primary panels — welding needs controlled conditions and calibrated equipment. On-site repairs are routine, though: patch kits and handheld welders fix punctures in place, and a single cushion can be swapped in a few hours. Order 2–3 spare cushions with your kit.
DIY-adjacent option: raw ETFE film (100–250 μm) is purchasable by the roll, and small
builders have made cushions with impulse sealers. It's a real learning curve on seams and patterning —
treat it as a fallback, not the plan of record.
3. Container math — why this concept works
Your instinct is right: this is one of the few enclosure types whose volume when shipped is nearly independent of its volume when assembled.
Worked example: 50 ft (15.2 m) dome3V geometry, ~5/9 sphere · floor area ~182 m² (~1,960 ft²)
· envelope ~300 m² · interior volume ~900+ m³
Cushions~75 triangles, ~4 m² each, edges ~2.6–3.1 m · folded weight ~1–1.5 kg/m²
· whole cladding packs into ~2–4 pallets
Structure~165 struts, longest ~3.1 m (3V) — easily fits a 40 ft container's 12 m length;
aluminum kit estimated ~1.5–3 t
40 ft HC container12.03 × 2.35 × 2.70 m, ~76 m³, payload ~26–28 t —
dome kit + cushions + inflation units + spares + tools fit with room to spare
| Frequency (50 ft dome) | Panels | Struts | Max panel edge | Trade-off |
|---|---|---|---|---|
| 2V | ~40 | 65 | ~4.7 m | Fewer, very large cushions; simplest frame |
| 3V | ~75 | ~165 | ~3.1 m | Best balance; standard choice for this size |
| 4V | ~160 | ~250 | ~2.4 m | Finer triangles, more even cladding, more labor |
Counts are approximate and depend on dome fraction (3/8 vs 5/9) and hub design.
4. How expensive? (ballpark, get real quotes)
Caveat: small one-off orders price at the high end of any range. These are
order-of-magnitude planning figures, not quotes; the ETFE market moves and Asian vs Western
fabricators differ by 2–3×.
| Item | Ballpark cost | Notes |
|---|---|---|
| Cushion system incl. clamp extrusions & gaskets (Asia-supplied) | ~$80–180 per m² of envelope | ~300 m² dome → ~$25k–55k; a ~4 m² triangle cushion ≈ $350–800 |
| Same from Western specialist | ~$200–400+ per m² | ~$60k–120k for the same area; stronger engineering support |
| Pattern engineering / setup (one-off) | $3k–15k | Amortized across the few unique panel types |
| Inflation & control units (primary + backup, with dryer) | $5k–20k | Consumes ~100–400 W continuously |
| Aluminum geodesic structure kit (engineered, marine-grade finish) | ~$25k–80k | DIY steel (EMT/conduit) alternatives cost far less but corrode |
| Lead time | 8–16 weeks | Pattern engineering 2–4 wk + fabrication 6–10 wk + shipping |
Realistic all-in envelope (cladding + structure + inflation, your own labor): ~$50k–190k for a 50 ft dome, with the Asian-supplied route near the bottom of that band.
5. Material & performance options
ETFE is tunable mainly through layer count (insulation), printing/fritting (shading), and color/tints. Typical values:
| Option | Appearance | Light transmission | Solar heat gain (g) | U-value (W/m²K) | Notes |
|---|---|---|---|---|---|
| Clear, 2-layer | Glass-clear | ~85–90% | ~0.7–0.8 | ~2.6–3.0 | Best for solar-through applications |
| Clear, 3-layer | Very clear | ~75–85% | ~0.6–0.7 | ~1.8–2.2 | Common default for occupied roofs |
| 4–5 layers + low-e coating | Clear | ~65–75% | ~0.4–0.6 | ~1.0–1.4 | Cold-climate / energy focus |
| Frit-printed dots/stripes | Semi-transparent, tunable | Set by print density (e.g. 20–70%) | ~0.3–0.6 | as base | The standard shading strategy; any density, any pattern |
| Translucent white / opaque | Diffusing or solid | 0–60% | low | as base | Good below the living sightlines |
| Tinted / colored film | Bronze, blue, etc. | Reduced | Reduced | as base | Also full-color printed graphics |
| Aerogel-laminated ETFE | Milky, high-diffuse | ~20–50% diffuse | low | ~0.8–1.2 | Premium translucent super-insulation |
Alternative materials worth knowing
- PVC/polyester cushions — $30–80/m², same inflation hardware, but ~10–15 yr UV life. Budget path.
- PTFE-coated fiberglass — opaque, extremely durable (25–30+ yr), used for tension structures.
- Polycarbonate multiwall — rigid, cheap, insulating; ships as bulky sheets, which hurts your container math.
- Glass — weight (~25–50 kg/m²) and fragility make it a poor fit for ocean shipping + dome geometry.
6. Service life & replacement
- ETFE film: exceptionally UV- and chemical-stable. Expected service life 25–35+ years; standard warranties run 10–15 years. Eden Project's original cushions (2001) are still in service.
- Reality of "replacement": envelopes are usually maintained, not replaced wholesale. Individual cushions get swapped after damage (impact, vandalism, seal failure) using the same clamp rails — hours of work, not weeks. Film replacement while reusing frames is also possible.
- Wear items to plan for: inflation blowers and air dryers (service/replace every ~5–10 yr), EPDM gaskets (~15–20 yr), filters/desiccant (consumable).
- Self-cleaning: ETFE's anti-adhesive surface sheds dirt in rain — a genuine advantage over glass at sea, where a freshwater rinse is precious.
- Failure mode is gentle: a punctured cushion slowly deflates and drapes; it does not shatter or unzip the building. A blower outage takes hours to matter, and backup blowers + battery cover it.
7. Flexible solar panels inside a clear dome
Framework: compare identical panels inside vs. outside, so the panel's own losses cancel out. The dome adds losses from five sources:
| Loss mechanism | Typical penalty | Can you mitigate? |
|---|---|---|
| Reflection at film/air interfaces (2-layer cushion: 4 surfaces; 3-layer: 6) | 2-layer: −12%; 3-layer: −19%; 4-layer: −26% | Use clear 2-layer cushions for the triangles above the array |
| Frit / printing in the light path | ~−0.85 × print coverage | Order those specific triangles un-printed |
| Strut & hub shading of the sky | −5–15% | Place array high, aligned between strut sightlines |
| Mounting geometry (can't tilt/track ideally inside) | 0–15% (small in tropics where sun is high; worse at high latitudes) | Near-top placement on a south-facing (N-hemisphere) slope |
| Heat (less convective cooling inside) + salt film on cushion | −5–10% combined | Ventilate the panel zone; rinse the dome (rainwater catch!) |
| Net result | ~60–80% of outdoor output (plan on ~65–70%) |
Synergy worth noting: premium flexible panels already use ETFE as their front sheet, so there's no material-compatibility concern, and clear ETFE transmits the UV/blue spectrum panels can use.
Interactive estimate
Estimated output inside vs. outside: — of outdoor yield · Outside: — kWh/day → Inside: — kWh/day
Ways to claw back yield
- Hybrid triangles: replace 10–20 cushions with rigid glass panels mounted in the same clamp extrusions — those get full outdoor output while wiring stays inside. Still ships flat.
- External mount on selected cushions: flexible panels are ~3 kg/m²; some designs laminate/fix them on top of specific cushions → ~90–95% of outdoor output with partial protection.
- Bifacial bonus: white/opaque lower cushions + reflective deck under bifacial flexible modules can add ~5–10% from interior albedo.
- Remember the blower tab: inflation runs ~100–400 W continuous (~2–8 kWh/day) — budget ~1–3% of production.
8. Marine / seastead-specific checklist
- Corrosion: ETFE shrugs off salt. The risk is the frame: anodized marine-grade aluminum extrusions, 316 (or duplex) stainless fasteners, isolation washers/tape between dissimilar metals, and greased gasket channels.
- Wind: a dome is close to the ideal aerodynamic shape; cushions are light (1–1.5 kg/m²) so uplift and debris loads are modest. Storm mode = raise cushion pressure.
- Condensation: inflation air is dried (prevents fogging between layers); also design night-time interior ventilation, or the inner film will drip at dawn.
- Rain noise: drumming on foil cushions is loud. Fritted/upper-layer texture and interior soft finishes help; the plus side — the dome is a perfect rainwater catchment.
- UV inside: clear ETFE transmits UV well; choose UV-stable interior materials and remember occupants can sunburn indoors.
- Fire: ETFE melts and shrinks away from flame (self-venting) rather than burning aggressively — but it's a plastic envelope; plan egress hatches at the base.
- Assembly at sea: 3–5 people, ~1–2 weeks for a 15 m dome; a gin-pole or small crane helps for the top rings. Do final cushion fitting in calm weather.
9. Bottom line
- A 50 ft ETFE-cushion dome genuinely ships in one 40 ft container — cladding folds to a few pallets, structure nests as stock lengths, and it yields ~180 m² of floor and ~900 m³ of volume.
- Panels are custom but highly repetitive (2–3 unique triangles), fabricated off-site with pattern engineering from your dome geometry; expect ~8–16 week lead time and roughly $50k–190k all-in for envelope + structure + inflation (wide range; get three quotes).
- Plan on 25–35 years from the film with component-level maintenance, not wholesale replacement.
- Indoor solar costs you roughly a third of your yield (~65–70% of outdoor) — a fair price for salt-spray and typhoon protection, and hybrid triangles can buy most of it back.