Everything you need to know about building and renovating with straw bales
External Wall Insulation, or “Wrapping”
Insulating external façades with construction straw bales — natural, vapour-open and highly effective.
Construction straw bales are ideal for insulating external façades — as a continuous, high-performance insulation layer in timber or solid structural systems, as well as in load-bearing straw bale construction. They significantly reduce heat loss and help maintain comfortable indoor temperatures in both winter and summer.
The straw insulation is protected on the outside with a vapour-open plaster system, such as lime or clay plaster. This allows moisture to regulate naturally without causing water to accumulate within the structure. The solution also stands out for its environmental performance: a regional, renewable raw material with CO₂ storage benefits.
Internal Wall Insulation
More peace and quiet, a healthier indoor climate, and natural insulation — without synthetic additives.
Construction straw bales are also suitable for insulating internal walls — wherever acoustic comfort, a stable indoor climate, and an ecological solution are required. The bales can be used as an insulation layer in suitable wall systems and create a noticeably more comfortable indoor atmosphere.
In combination with vapour-open surface finishes such as clay or lime plaster, the construction remains breathable and can regulate moisture effectively. This improves living comfort, reduces reverberation, and supports a healthy indoor climate — ideal for living spaces, offices, or partition walls with higher comfort requirements.
Roof Insulation
High-performance insulation from the inside — warm in winter, noticeably cooler in summer.
Construction straw is exceptionally well suited for roof insulation, especially when installed on the inside of the roof, for example between rafters or within suitable roof build-ups. This keeps heat reliably inside the building during winter, while its high thermal storage capacity provides significantly better protection against summer heat, helping rooms overheat more slowly.
A vapour-open construction is essential so that moisture can be regulated safely. Combined with the right layers and careful workmanship, this creates a durable, comfortable roof structure — natural, efficient, and regional.
Floor and Ceiling Insulation
Less heat loss, more peace and quiet — naturally insulated between floors.
In intermediate floors and top-floor ceiling constructions, construction straw creates a highly effective insulation layer: less upward energy loss, significantly improved sound insulation, and a more balanced indoor climate. Especially in floors between living and sleeping areas, this noticeably reduces sound transmission.
Depending on the construction method, the bales are integrated into suitable assemblies and then protected accordingly. Clean installation with minimal gaps and a vapour-open design are essential to ensure the insulation remains permanently dry and performs reliably over time.
But ....
“Isn’t straw extremely flammable?”
No. Densely compressed construction straw contains very little oxygen. When installed professionally, straw insulation systems can achieve very high fire-resistance performance values (reaction to fire: Class E, fire resistance class: REI90) and can withstand direct fire exposure for 90 minutes.
“Straw houses must attract lots of insects and mice.”
No. Construction straw is dry, densely compressed, and fully enclosed. It offers neither food nor habitat for insects or rodents.
“Doesn’t the straw contain pesticides that are harmful to health?”
No. On the contrary: measurements and studies indicate that buildings made with straw can in some cases contain comparable or even lower pollutant concentrations than conventional buildings — provided the material selection and construction quality meet standard quality requirements.
“Straw is not stable enough for long-term construction.”
No. Straw bale construction has been used successfully for well over 100 years. In combination with timber or solid structural systems, it creates durable and structurally safe buildings. The material also offers high ductility, which means straw bale construction can absorb more deformation during earthquakes and is in many cases considered more earthquake-resistant than conventional, more brittle construction methods.
“Doesn’t straw rot over time?”
No. Moisture protection is the key. If straw remains permanently dry, it is extremely durable — there are straw buildings more than 100 years old that still look as good as new.
“You can’t build modern houses with straw.”
No. Straw insulation allows for a high degree of architectural freedom — from single-family homes and multi-storey buildings to passive house standards. With the right construction methods and plaster systems, even curved forms, organic geometries, and dome structures are possible.
“Isn’t this just for eco-idealists?”
No. Straw is a high-performance regional building material that is both ecologically sound and economically competitive.
Technical Data — Construction Straw Bales
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Product / raw material: Organic construction straw bales, 100% organic wheat straw
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Approval: ETA-10/0032
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Bulk density: 95–167 kg/m³
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Thermal conductivity (declared value):
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λD = 0.046 W/(m·K) depending on installation orientation
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λD = 0.082 W/(m·K) depending on installation orientation
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Thermal conductivity (design value):
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λr = 0.050 W/(m·K)
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λr = 0.085 W/(m·K)
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Reaction to fire: Class E
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Short-term water absorption: Wpa = 7 kg/m² at a bulk density of 105 kg/m³
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Available insulation thicknesses: 260–1200 mm
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Bale formats (H × W):
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260 × 420 mm
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320 × 420 mm
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360 × 490 mm
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370 × 830 mm
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500 × 830 mm
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Bale length: custom-made, 450–2000 mm
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Specific heat capacity: c = 2000 J/kg·K
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Vapour diffusion resistance: μ ≤ 5
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Moisture content of raw material: < 15%
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Raw material quality values: weed content < 0.5 wt.%, residual grain content < 0.4 wt.%
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Mould resistance: 2
