Performance comparison between building insulating materials made of straw bales and EPS for timber walls

This paper studies the thermal and acoustic performance of straw bale walls used in timber-frame semi-detached houses recently built in Sicily (Southern Italy), and compares them to similar walls where expanded polystyrene (EPS) is adopted in place of the straw bales. In-situ measurements were carried out to analyse the acoustic performance of both wall typologies. The weighted Apparent Sound Reduction Index for the partition wall between two houses, as well as the weighted Standardized Level Difference for the façades were assessed based on the ISO Standards 16283. Moreover, the two insulating solutions were compared in relation to their steady and dynamic thermal performance. The results underline that the acoustic performance of the straw bale walls is far better than the walls adopting traditional EPS insulation. However, slight improvements are suggested to further increase the sound insulation properties of straw bales. On the other hand, EPS is a more effective thermal insulation even if straw bale walls comply with Italian standards. Finally, the dynamic performance of straw bales should be improved by increasing their density. Overall, the proposed straw bales used can be conveniently used in low-energy and n-ZEB buildings in warm and mild countries.