Straw bale construction towards nearly-zero energy building design with low carbon emission in northern China

Abstract

With the aim of achieving carbon neutrality, bio-based construction is of increasing interest for decarbonization globally. Among the potential candidates, straw bale is promising due to its ready availability and energy efficiency benefits. However, thermal conductivities of straw bales can vary greatly due to construction details, which may lead to failures in meeting nearly-zero energy building (nZEB) design standards in real practice. In the context, this study applied thermal property and carbon emission assessment of full-size straw bale walls (SBWs) and construction of an experimental building in northern China. The results demonstrated that the thermal conductivities of different monitoring portions of the SBWs ranged from 0.067 to 0.088 W·m−1·K−1. This resulted in U-values (0.16 W·m−2·K−1) marginally higher than the lower limits of nZEB design, indicating the importance of addressing thermal bridging issues of SBWs. The SBWs without additional insulation layers therefore can satisfy nZEB design standards in the severe cold region after certain adjustments. Besides, when not accounting for carbon sequestration, SBWs generated the lowest emissions among the schemes in meeting U-value limits for nZEB design (at least 14.6% lower than those of timber walls), with increasing emission reductions as U-value limit decreased. The results indicated that SBW demonstrated effectiveness in carbon reductions with high thermal performance. The findings of the research can facilitate application of straw bales and development of clean construction and net-zero design in northern China.