Thermal Insulation based on Natural Fibers for Sustainable Buildings

The buildings sector contributes approximately 40% of global carbon dioxide emissions annually. As buildings lower their operational carbon footprint, embodied carbon contributes over 50% to the emissions of high-efficiency buildings. Most embodied carbon is emitted during raw material extraction, transport, and product manufacturing. Insulation is the second largest contributor of embodied emissions in residential buildings after concrete, and the manufacturing of insulation materials, like extruded polystyrene (XPS), involves emissions that contribute to their global warming potential (GWP). Although many studies have investigated bio-based alternatives, further development is required to achieve sustainable insulation materials. Plants sequester carbon dioxide as they grow, and their inherently porous structure makes them a promising feedstock for thermal insulation that can be carbon negative. This research develops insulation composites comprising industrial hemp and kenaf plant fibers with polylactic acid (PLA) and cellulose diacetate (CDA) binders. The fiber properties and insulation performance of the composites as a function of varying binder weights and densities are investigated. The manufacturing process of the lab-scale insulation encourages the entrapment of air, minimizes energy and water consumption, and is inspired by airlaid web forming processes used for nonwovens. Hygrothermal and physical characterization of the fibers was performed using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and other techniques. The thermal conductivity (k) of the fabricated samples was measured using the modified transient plane source (MTPS) technique. Overall, the insulation performance of the developed composites is comparable to commercial insulation, with k values ranging from 0.037 to 0.043 W/m-K. Future work must ensure that this insulation meets flammability and other standards. Nevertheless, this plant-based insulation is a promising pathway to reduce embodied carbon in buildings.