This study addresses two critical challenges in advancing a sustain-able and circular economy. The construction industry must transition to low-impact materials, as many conventional insulation materials deplete finite resources and have high embodied carbon. Sustainable, effective alternatives are essential to reduce both operational and embodied carbon of buildings. Concurrently, the world faces an increasing volume of waste; recycling options are often preferable to landfill and incineration but can impose environmental burdens. One problematic material is waste polylaminate carton (e.g. Tetra-Pak) which cannot be easily recycled alongside paper products, with the recycling process complex and region-dependent. Mycelium-based composites (MBCs) have emerged as a promising bio-based material capable of transforming lignocellulosic waste into effective insulation products. In their manufacture, fungal mycelium grows on a substrate, forming a natural adhesive as it colonises the material. Once fully colonised, the material is dried to kill the fungus and produce an inert material. While agricultural byproducts, such as straw and hemp-shiv, are common substrate choices, fungi can also grow on more complex waste streams, including polylaminate materials. In this study, the successful growth and binding of polylaminate waste with mycelium to produce MBCs is demonstrated. MBCs were produced using Lentinus tigrinus mycelium with hemp-polylaminate blends in ratios (by mass of hemp:polylaminate) of 1:0, 2:1, 1:2, and 0:1. Thermal conductivity (λ) measurements were conducted, with the measured thermal conductivity of the pure polylaminate MBCs λ = 0.035 ± 0.002 W/mK. Furthermore, increasing the proportion of polylaminate in the substrate blend did not significantly affect λ. Water absorption properties were also evaluated, showing that higher Tetra-Pak content led to reduced water absorption. Additionally, a life cycle assessment (LCA) was conducted, revealing that these materials exhibit a low global warming potential (GWP), suggesting they could be low-carbon alternative to conventional insulation. These findings highlight the potential of utilising complex waste streams from the food and beverage industry to produce mycelium-based insulation materials. This approach contributes to reducing environmental burdens associated with waste while promoting circular and sustainable practices within the construction sector.