Development of modular parts for clay-passive houses

Development of extensive storey-high modular parts made of renewable primary products (wood, straw, hemp) for clay-passive houses.

Content Description




The structure of the prefabricated, large sized wall-, platform- and rooftop modular parts consists from a timber frame construction which is optimized for thermal insulation with straw. The indoor-plaster is made from biofibre loam-plaster (an EU patended type of clay-plaster). The outside surface of the wall parts consists from an 8 cm layer of biofibre loam.

An unbroken covering of the modular parts in sizes up to 8 x 3,2 m with a special clay-fleece layer causes permanent capillary desiccation of the natural insulation material in the modular parts of the building also of the platform parts due to the strip foundations. As a multifunctional layer it causes as well an airtight covering, acts as vapour barrier and wind barrier and buffers moisture. The fitting of the strawbale material and drying of the ready made modular parts is done in shop, safe from weather damages.

The most important steps of development were:

  • Dimensioning of the load bearing structure and the modular parts for transport on road and rail and for the most efficient way of using suitable types of strawbales for thermal insulation.
  • Development of technologies for industrial production of clay-passive modular parts by optimizing the mixing technology for fibres and clay or loam and for the way of covering modular parts with clay or loam.
  • The development of a compound from clay and fibres for an airtight but capillary active lining of surfaces of massive wood (boards, log walls). The final airtightness is reached by the compound with a layer of clay plaster. The effectiveness of this clay-fleece technology was proofed by testing a small test-chamber in the Arsenal Research Center in Vienna and with Blower-Door tests in a prototype passive house building.
  • To prove that a concept of a capillary active airtight occlusion of not processed straw between two layers of clay in outer walls can work without occurrence of condensate water inside the building component. This was proofed by measurements of behaviour of moisture in different varieties of constructions of a building block unit and with long time measurements in the building block units of a demonstration building.


The basic concept of prefabrication of large sized modular parts has appeared to be optimal for the clay/wood/straw passive house construction. The natur & lehm company made valuable findings on construction details for increasing the degree of prefabrication and for reducing costs for further production.

Beeing adapted to local economic and ressource conditions this system has promising aspects also outside Central Europe. Even for example in South Asia there a quite surprising opportunity appeared to replace timber in this energy efficient building system with innovative renewable construction materials from bamboo. This looks promising from economic as well as from environmental point of view.

The overall efficiency of the system developed from these modular parts can be judged by the outcomes of building the first demonstration building, the "Clay-Passive House Tattendorf" (see report on this "House of the Future" project "Lehm-Passiv Bürohaus Tattendorf").

Project Partners

Project leader:

Roland Meingast
Fa. natur&lehm Lehmbaustoffe GmbH

Project partners:

  • Arch. Prof. Dipl.Ing.Wolfgang Reinberg, Architekturbüro Reinberg
  • Ing. Werner Vogel; Managementbüro für Forschung und Entwicklung
  • Ing. Erich Longin; Fa. Longin Holzbau GmbH
  • Franz u. Andreas Zöchbauer, Fa. Zöchbauer
  • Ing. Payerl; Fa. Fex, Öko-Faserverarbeitung
  • Waldviertler Flachshaus Gmbh
  • Arch. Bernhard Oberrauch


Roland Meingast
natur&lehm Lehmbaustoffe GmbH
Oberwaltersdorferstraße 2 c, A-2523 Tattendorf
Tel.: 0043/2253/81 030/0
Fax: 0043/2253/81 030/18