Energy efficiency, energy saving, recycling and reuse of materials and reducing the harmful impact of buildings on the environment, influence the idea of ​​implementing composites that include ecological matrixes in daily construction operations, using natural or recycled materials. Straw is a widely available by-product of agricultural activity. By recognizing the properties of the straw, as well as other agro-waste materials, a new dimension is given to the thermal insulation of buildings. Furthermore, the building becomes highly efficient, sustainable and with lower costs.

Standardized samples of cement composites were tested and analysed, with partial replacement of the first fraction of the aggregate with straw in the range of 5%, 10%, 20% and 50%, with emphasis on the thermal properties. Thermal conductivity decreases with an increase in the percentage of straw in the cement composite. The average value for thermal conductivity for all samples is 0.310 W/m⋅K. The recipe with a share of 20% straw as a substitute for the smallest aggregate, proved to be the most suitable recipe, which also showed good mechanical properties. Its thermal conductivity is l = 0.223 W/m⋅K, that is about 10 times lower than the thermal conductivity of ordinary concrete. However, with an increase in the percentage of straw, the compressive strength decreases. Therefore, the application of this type of material is limited to non-bearing structural elements.