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This paper provides an overview of the principal earthen building materials of Central Asia and the cultural aspects of a traditional architecture which incorporates an understanding which dates back centuries. The work was started by focusing on sets of research questions which also helped to structure the study: what are the manufacturing processes of materials in the area? Based on the analysis of materials, what suggestions can be made for a more appropriate conservation of the Central Asian built heritage? There is at present a large lacuna in the literature on Central Asian materials. The traditional processes of production and the traditional methods for repairing require proper documentation. Several craftsmen were interviewed by the author in order to collect data on the traditional process of manufacturing earthen materials. The aim of interviewing local craftsmen through semi-structured interviews was to increase the scant information about the local, traditional techniques of construction and the materials employed.

Ajina Tepa is one of the most important archeological sites in central Asia and it was fully excavated in the 1960s with modern documentation techniques. The UNESCO/Japan Trust Fund project 'Preservation of the Buddhist Monastry of Ajina Tepa, Tajikistan' started in 2005 and will be completed in 2008. Being scientific documentation one of the project aims, three-dimensional mapping of the walls and geomorphological mapping of the whole site were carried out. Digital stereo-photogrammetric techniques were applied to record the surface morphology of the earthen walls. Presently the walls are heavily eroded, especially if compared to their outline as recorded in the 1960s. In addition, the top part of the damaged wall is rounded, and the basal part shows the typical erosional pattern known as coving. Wind and rain are responsible for the decay of top parts and hence their rounded shape. At the bottom, salt attack causes erosion in combination with abrasion caused by wind and windblown silt.When the wall loses its strength against its own load, the upper and middle part of the wall collapses suddenly. Digital photogrammetric techniques are extremely useful for documenting such phenomenon and the shape of the wall before collapsing. It is ascertained here that such monitoring system supplies basic data to take measures for preventing collapse.

The use of hemp-lime as a construction technique is a novel approach which combines renewable low carbon materials with exceptional hygrothermal performance. The hemp plant can grow up to 4m over a four month period, with a low fertilizer and irrigation demand, making it very efficient in the use of time and material resources. All parts of the plant can be used -the seed for food stuffs, the fibre surrounding the stem for paper, clothing and resin reinforcement, and the woody core of the stem as animal bedding and aggregate in hemp-lime construction. The unique pore structure of the woody core (shiv) confers low thermal conductivity and thermal and hygric buffering to hemp-lime. The construction technique promotes good air tightness and minimal thermal bridging within the building envelope. All these factors combine to produce low carbon, hygrothermally efficient buildings which are low energy both in construction and in use, and offer opportunities for recycling at end of life. This paper reports on the hygrothermal performance of an experimental hemp-lime building, and on the development of a computerized environmental model which takes account of the phase change effects seen in hemp-lime.

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