Evaluation of the acoustic and environmental performance of different wall structures with particular emphasis on straw

Abstract

The building material straw as a renewable and almost endlessly available by-product could contribute to lower greenhouse gas emissions and primary energy consumption in the building construction sector. Straw as building material, is used as insulation material in metal stud walls and timber frame constructions. Additionally, whole straw bales can be used as insulation and bearing structure in combination with a timber frame. The state of the art provides an inconsistent data conglomerate on the acoustical and environmental performance of different wall structures, test setups and assessment methods. The presented research shows results of a parallel evaluation of the acoustic and environmental performance of wall structures with a consistent approach in measurement and calculation methods. The results of building acoustic measurements are used to quantify the acoustic potential for of straw in those wall constructions. The results show that the building acoustic performance of wall constructions with straw is comparable to the performance of already on the market established wall constructions. The influence of parameters like density, dynamic stiffness, air flow resistivity and longitudinal wave speed of used materials on the measured sound reduction index is discussed. Especially the density and the dynamic stiffness are important material parameters to achieve a high sound reduction index of the wall constructions. Since straw is a renewable material, the environmental impacts of the different acoustically analyzed wall constructions were investigated additionally. Standardized assessment methodologies were applied on the different components and a comparison with different insulation materials was carried out. It could be shown that the use of straw leads to lower environmental impacts (demonstrated in the Global Warming Potential indicator), though, the insulation material is not the most relevant parameter of the structures. Significantly higher environmental impacts are caused by the bearing structure (metal and timber frame studs) and the planking materials. Finally, an overall comparison together with standard concrete and brick wall structures underlines the beneficial environmental properties of walls made of renewable materials with straw.