Biospiral house



The Biospiral House of the Terra Purna project consists of a collaborative research project in sustainable architecture and bioconstruction. It aims to study the best techniques and materials to obtain healthy, confortable and aesthetically inspiring houses dwellings with a tendency towards zero environmental impact and thus suitable for places with high environmental constraints, such as the case of natural parks or ZEPAs.

It is a passive integral solar house with a green roof that maintains high levels of comfort. It does not need to be heated in the winter nor cooled in the summer, maintains high indoor air quality, produces its own energy and treats its residues. In order to do this, bioclimatic architecture and the careful selection of the building elements with respect to their cardinal function and disposition are used, for example, a strong thermal mass in the south using a cob wall and strong insulation with a wall of straw bales in the north face.

In addition to the production of energy-efficient housing, this project also aims to study the best techniques to reduce environmental impact in relation to its total life cycle, in other words, from construction to end of life. For this reason all the water and electricity used in the construction of the Biospiral House is obtained and produced locally and the vast majority of materials are absolutely biodegradable and locally available.


The Biospiral House being an experimental house intends to generate and share knowledge about sustainable housing and thus establish models and references for the creation of a sustainable future.


Building Information:

  •     Area: 60 m2
  •     Foundations: Dry stone on site
  •     Structure: Locally acquired chestnut wood
  •     North wall: 180 straw bales / Provenance: S. Vicente de Alcántara (18 km)
  •     South wall: 7 m3 of clay / Provenance: Aceña de la Borrega (4,5 km)
  •     Plasters: Clay and lime
  •     Roof lining: Local cane reeds
  •     Waterproof fabric: EPDM Giscolen
  •     Insulation cover and floor: Local cork
  •     Wood treatment: Natural linseed oil without drying agents
  •     Water for construction: Local water source
  •     Electricity for construction: Local photovoltaic production
  •     Toilet Crockery: Reused from neighbours and salvaged
  •     Confragens: Wood salvaged from Valéncia de Alcántara recycling point
  •     Phyto-treatment of black and gray waters
  •     Labour: National and international volunteers fed by local organic agricultural production