- REEDOME
- The dome guide
- Stage 2: Understand
- 1. Discover
- 2. Understand
- 3. Decide
- 4. The path
Updated 2026-11-03
Short answer: reed-thatch, foam (EPS) and glass domes differ in material, warmth, upkeep and weight, not in shape. Reed is a natural, breathable covering with the longest track record in Europe. An EPS foam shell is an industrial, light and long-lasting material, but it is combustible, and its fire class depends on additives (BPF/Designing Buildings, 2018-04-16). A glass dome lets in the most light, but insulates worst of the three.
All three can be built as geodesic domes, because shape and shell material are two separate choices. REEDOME works with only one of them: a geodesic timber frame covered in reed. Below is how the materials actually differ, so you can compare them on more than looks.
What is the difference between a reed, foam and glass dome?
The difference starts with what the shell has to do. A reed roof and the insulation beneath it work together as one system. A foam shell is usually a self-contained structural sandwich panel: an EPS core between rigid outer and inner faces. A glass dome barely insulates at all. It lets heat and light pass both ways, so the glazing unit itself has to carry the insulation job.
| Criterion | Reed dome | Foam (EPS) dome | Glass dome | Source | Date |
|---|---|---|---|---|---|
| Main insulation | Wood fibre/cellulose under the reed, up to 30 cm | EPS core in the shell itself, 14–18 cm in typical kits | Glazing unit (double or triple) | Manufacturer specifications (common market practice) | 2026 |
| Typical U-value/conductivity | Depends on the full layer build-up, designed for class A++ | EPS conductivity around 0.03–0.04 W/(m·K); thickness sets the U-value | Double glazing U-value ~1.2–3.0 W/(m²·K), triple ~0.5–1.2 W/(m²·K) | General glazing industry technical literature | 2026 |
| Fire class | Reed burns; risk is managed with a non-combustible layer and fire-retardant treatment | EPS is combustible; with fire-retardant additives it reaches Euroclass E, without them it performs worse | Glass itself is non-combustible, but the frame and seals can burn | BPF / Designing Buildings, "Ten facts about EPS insulation" | 2018-04-16 |
| Expected lifespan | About 50 years with a suitable pitch and upkeep | Decades, if the shell is protected from UV and water | Glass itself lasts a long time, but seals and gaskets are usually replaced sooner | Dutch thatchers' federation (reed); general construction-practice literature (EPS, glass) | 2026 |
| Maintenance | Periodic inspection, clearing leaves, renewing fire-retardant treatment | Inspecting the outer protective coating, renewing sealing | Regular cleaning (twice a year recommended), replacing gaskets and seals | General building-maintenance practice | 2026 |
| Relative weight | Medium: reed layer plus insulation | Lightest: EPS density around 28–32 kg/m³ | Heaviest: a glazing unit weighs around 22–25 kg/m² per layer | Glass industry weight calculators; EPS density specifications | 2026 |
| Insurance | In the Netherlands, a distinct line item; premiums can be higher | Treated as an ordinary industrial cladding | Treated as ordinary glazing | verzekeraars.nl, "Rieten daken" brochure | – |
This table shows general tendencies, not exact REEDOME figures. Our actual U-values and fire class depend on the whole wall/roof build-up, not one material alone, and we do not publish them here without separate engineering sign-off.
Which dome stays warmest in winter?
It depends on the whole shell, not one material. A reed dome with a thick insulation layer beneath the thatch is designed so the whole house reaches energy class A++, which requires an air-change rate no higher than 0.6 per hour at 50 Pa pressure difference (STR 2.01.02:2016, in force since 2021-01-01). A foam shell can reach similar thermal conductivity if the core is thick enough, but its airtightness depends on the quality of the panel joints.
A glass dome clearly loses here. Even the best triple-glazed U-value is worse than a typical insulated wall's U-value, because a window always lets through more heat than an opaque, thickly insulated wall. A dome clad mostly in glass therefore needs more heating energy in winter than a reed or foam dome of the same floor area.
Does reed thatch catch fire more easily than foam?
Both materials are combustible in their own way. Reed burns like any plant material, so the risk is managed with a non-combustible layer under the thatch and periodic fire-retardant treatment. EPS is also combustible: without fire-retardant additives its reaction to fire is worse, and with additives the industry reports Euroclass E (BPF/Designing Buildings, 2018-04-16). In both cases the final fire class of a wall or roof depends on the whole layer build-up with its protective layers, not on one material in isolation.
We do not publish a specific fire-safety class for REEDOME domes here. That claim is waiting on sign-off from a fire-safety specialist (see the rules in patvirtinta.md).
Which option is lightest to build?
By material weight, the foam shell is lightest: typical EPS density in building panels is around 28–32 kg/m³, so the whole structure can be lighter on the foundations and frame. Glazing units are heaviest; one square metre of double glazing weighs around 22 kg, so a glass dome's frame has to be stronger, usually steel. A reed dome sits between the two: the thatch and insulation add weight, but the frame stays timber.
How is each dome type maintained?
- Reed dome. Regular inspection, clearing leaves and moss, renewing the fire-retardant treatment on the manufacturer's schedule. More on this in “How long does a thatched roof last”.
- Foam dome. Checking the outer protective coating (render or paint), since that is what shields the EPS core from UV and water. Damaged coating means the foam underneath starts to degrade.
- Glass dome. Regular cleaning and checking seals and gaskets. A failed glazing-unit seal usually shows up as condensation or moisture between the panes, and the unit then needs replacing.
Why REEDOME chooses reed, not foam or glass
REEDOME builds only geodesic domes. There is no stick-frame or sandwich-panel version. On a geodesic timber frame we lay 30–35 cm of hand-laid reed, with up to 30 cm of wood-fibre or cellulose insulation beneath it. It is a pairing of natural materials with a long, well-studied history around the Baltic and North Sea, covered in more detail in “Reed thatch: a tradition making a comeback”. The geometry itself, a triangular network spreading structural loads, is explained in “Why a geodesic dome is so strong”, and the energy class is covered in “An A++ dome: warmth, ventilation and running costs”.
See all REEDOME models and sizes on the domes page.
Frequently asked questions
Can you build a dome from glass instead of reed?
Technically yes. Some manufacturers build fully glazed geodesic domes, usually as conservatories or showcase spaces. For a year-round home, that means weaker thermal insulation and higher winter heating costs. REEDOME does not build this type of dome.
Is a foam dome cheaper than a reed dome?
We do not compare specific prices here, because REEDOME's prices depend on size, plot and finish, not only on the shell material. General construction practice shows that an industrial EPS shell is often cheaper to produce at scale, but that does not necessarily mean a cheaper finished home.
Which dome type lasts longest?
All three materials can last decades if properly maintained. A reed roof lasts around 50 years with a suitable pitch and upkeep. An EPS shell lasts a long time if protected from UV and moisture. A glazing unit's service life is usually limited not by the glass itself but by its seals and gaskets.
Does a reed roof need more maintenance than foam or glass?
A reed roof needs periodic inspection and occasional renewal of fire-retardant treatment. A foam shell needs its outer protective coating checked. A glass dome needs regular cleaning and seal upkeep. None of the three is maintenance-free.
Which dome suits year-round living in a cold climate best?
For a permanent home, winter warmth, airtightness and energy class A++ matter most. A reed dome with a thick insulation layer meets that best of the three, because it does not depend on large glazed areas, which lose the most heat in winter.
Want to compare how different shells would suit your plot? Fill in a short enquiry and we will discuss your case together with our architect.
Sources
- BPF / Designing Buildings Wiki, "Ten facts about Expanded Polystyrene (EPS) insulation to help specifiers", last edited 2018-05-04 – designingbuildings.co.uk
- Platform Onderlinge Verzekeraars / verzekeraars.nl, "Rieten daken" brochure – verzekeraars.nl (in Dutch)
- STR 2.01.02:2016 (in force since 2021-01-01) – airtightness requirement for class A++ residential buildings, n50 ≤ 0.6 1/h.
This is general material-comparison information, not a technical or engineering assessment. An architect and structural engineer always verify exact U-values and fire class for your specific project.