The civil construction industry is responsible for a large part of the world’s energy consumption; therefore, in recent years, sustainable practices in this sector have become increasingly common to minimize the environmental impacts of civil construction during the life cycle of buildings. As a result, new materials and more sustainable building techniques are being sought. In Portugal, rice husk is an abundant agricultural waste with great potential to be used as a raw material in thermal insulation materials, as well as giant reed, which is considered an invasive plant. In this study, thermal insulation plates composed of rice husks and/or reed fiber were developed, using sodium silicate as a binder in various proportions and with dimensions of 30 × 30 × 3 cm and density ranging between 0.219 and 0.352 g/cm³. The main objective of the study is to evaluate the thermal characteristics of the plates, such as thermal conductivity, as well as the mechanical resistance to bending and water absorption. The results of the thermal conductivity tests were promising for all compositions, with values in the range between 0.0602 and 0.0745 W/m·K, meeting the requirements to be considered as thermal insulation materials. The results for bending strength and water absorption presented values within the expected range for materials of vegetal origin.

The paper presents results of analysis of thermal insulation materials based on plant fibers. It is suggested to use secondary raw materials of flax processing plants – flax noils – as a fiberfill in production of insulating slabs. The paper presents results of research on the microstructure of flax noils and flax fibers conducted using light microscopy and electron microscopy, respectively. A set of experiments aimed at determining physical and mechanical characteristics of thermal insulation materials has been conducted. Test results attest higher efficiency of the insulating slabs made from flax noils in comparison with flax fiber-based thermal insulation material. The main factors facilitating reduction of thermal conductivity coefficient of thermal insulation material made from flax noils have been determined.

The paper addresses the criteria ensuring a sustainable structure and efficiency of thermal insulation straw-boon slabs in full-scale conditions. Sorption humidity of heat insulator and conditions for fungus build-up on the surface of plant-based filler have been studied. Additives providing high water resistance of silicate glass used as the binder for thermal insulation material have been determined. Tests considering an array of technological parameters and fire behavior of straw-boon slabs confirmed a sustainable structure in the process of installation of thermal insulation material and in case of fire.

This study evaluates crushed bamboo as a coarse aggregate for structural–thermal wall composites, comparing its performance against mixes with wood sawdust and rice husk. Crushed bamboo was used in both smooth and surface-roughened conditions, where particle morphology and surface features were characterized by SEM and AFM methods. The roughened bamboo aggregate exhibited greater surface roughness, thereby improving interfacial adhesion with cement. Surface roughening increased 28-day compressive strength by ~39–44% relative to smooth particles. Incorporating fine plant-based fillers into cement–bamboo composites increased their compressive strength by ~33–75% and reduced thermal conductivity by ~12–18%, compared with the analogues without fine particles. Water-absorption tests on bamboo aggregate showed rapid uptake in the first 24 h (43–45%) and saturation after 7 days of ~65–70%, values lower than typical wood by-products, thereby helping to limit mix water demand. Findings indicate that crushed, surface-roughened bamboo, especially with fine bio-fillers, can produce sustainable wall materials with a strong balance between strength and insulation.