The development of new thermal insulation materials needs to evaluate properties and structure of raw material, technological factors that make influence on the thermal conductivity of material. One of the most promising raw materials for production of insulation material is straw. The use of natural fibres in insulation is closely linked to the ecological building sector, where selection of materials is based on factors including recyclable, renewable raw materials and low resource production techniques

http://dx.doi.org/10.5755/j01.ms.17.2.494

The efficiency of thermal insulation materials obtained from renewable resources depends on the possibilities of reducing thermal transfer via solid and gaseous conduction, thermal radiation and, in some cases, convection. The heat transfer mechanism for thermal insulation materials mostly depends on the structure and density of the material used. Efficient thermal insulation materials consist of a gaseous phase and a solid skeleton. Gas content in such materials can take more than 99% of material by volume. In this case, thermal transfer via solid conductivity is negligible. The current work analyses the possibilities of reducing heat transfer in the straw of a varying structure. For conducting experiments, barley straw was used. To evaluate the impact of straw stalk orientation in a specimen on thermal conductivity, strongly horizontally and vertically oriented specimens of straw stalks were prepared. To reduce heat transfer via gaseous conduction and convection in large cavities in straw stalks and between stalks, barley straw were chopped and defibered. In order to decrease heat transfer via radiation after thermal conductivity measurements, mechanically processed straw were coated with infrared absorbers. Due to thermal conductivity measurements of chopped and defibered straw, an optimal amount of infrared absorbers were determined.

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One of the essential requirements for buildings is energy saving and heat retention. About 40% of the total energy consumed in the European Union is used for heating of buildings. Most of the energy consumed in buildings is used for heating during the cold period and cooling during the warm period. A significant part of energy can be saved due to suitable insulation of buildings. More efficient energy saving can be ensured by using heat-insulating materials produced from renewable resources. In Lithuania straw is often used for making thermal insulation obtained with a thermal conductivity of 0.040 W/(mK). Straw thermal conductivity under different conditions as well as possibilities to use it for producing heat-insulating materials are analysed in the work.