The urgent global mandate to achieve net zero carbon emissions by 2030 has accelerated innovation in sustainable construction materials, particularly natural insulation solutions. This study addresses persistent challenges such as complex production processes, non-compostable components, and limited adherence to industry standards by developing and evaluating a novel slim insulation panel made from agricultural waste, specifically wheat straw. Targeted at retrofitting Grade 2 listed dwellings in the UK—where external modifications are restricted—the panels combine simplicity, full compostability, and conformity with regulatory benchmarks. Prototypes were fabricated using wheat straw and two compostable binders, tested for thermal performance, moisture stability, and biodegradability using an innovative Actual Wall Replication Method (AWRM) to mimic real-world conditions. The findings demonstrated superior thermal conductivity and durability, with panels achieving significant energy-saving potential without compromising heritage integrity. The work highlights wheat straw’s viability as an eco-friendly insulation material and accentuates the necessity of realistic testing for accurate performance assessment. This study offers a replicable framework for integrating circular economy principles into heritage retrofitting, bridging the gap between ambitious environmental targets and historic building preservation, thereby contributing to broader sustainable development goals.

The urgent global mandate to achieve net-zero carbon emissions by 2030 has accelerated innovation in sustainable construction materials, particularly natural insulation solutions. This study addresses persistent challenges such as complex production processes, non-compostable components, and limited adherence to industry standards by developing and evaluating a novel slim insulation panel made from agricultural waste, specifically wheat straw. Targeted at retrofitting Grade 2 Listed dwellings in the UK—where external modifications are restricted—the panels combine simplicity, full compostability, and conformity with regulatory benchmarks. Prototypes were fabricated using wheat straw and two compostable binders, tested for thermal performance, moisture stability, and biodegradability using an innovative Actual Wall Replication Method (AWRM) to mimic real-world conditions. Findings demonstrated superior thermal conductivity and durability, with panels achieving significant energy-saving potential without compromising heritage integrity. The work highlights wheat straw's viability as an eco-friendly insulation material and accentuates the necessity of realistic testing for accurate performance assessment. This study offers a replicable framework for integrating circular economy principles into heritage retrofitting, bridging the gap between ambitious environmental targets and historic building preservation, thereby contributing to broader sustainable development goals.