Biobased building materials continue to attract attention as the construction sector looks beyond carbon reduction alone towards circularity, healthy indoor environments and renewable resources. At Cardiff University’s Welsh School of Architecture, Dr Eshrar Latif is investigating how hemp-lime and Welsh sheep’s wool can be combined into high-performance building envelope systems that address these broader sustainability goals.

Rather than focusing solely on reducing operational carbon emissions, Dr Latif advocates a whole-life approach to sustainable architecture. This considers embodied carbon alongside circularity, biodiversity, health impacts and end-of-life performance. Such a perspective has guided his research into renewable construction materials throughout his academic career.

Optimising Hemp-Lime Composites

Dr Latif’s work builds on previous research into hemp fibre and hemp-lime, materials already recognised for their environmental performance. Hemp-lime combines industrial hemp shiv with a lime-based binder to create a lightweight composite that offers thermal insulation, moisture regulation and fire resistance.

The material also has a lower embodied carbon footprint than conventional cement-based products. Lime production generally generates less carbon than Portland cement, while hemp absorbs CO₂ during growth. In addition, the lime binder gradually carbonates throughout curing and service life by reacting with atmospheric carbon dioxide.

Current research focuses on improving the performance of hemp-lime through different material formulations. In collaboration with South Wales-based sustainable housing company Wellspring, Dr Latif developed five hemp-lime mixes and evaluated their water absorption, moisture buffering and moisture-dependent thermal conductivity. The findings informed the development of future wall panel systems incorporating hemp-lime insulation.

Welsh Sheep Wool as a Biobased Insulator

Building on this work, Dr Latif explored whether Welsh sheep’s wool could further improve the performance of hemp-lime wall systems while creating a new application for a declining local industry.

The proposed system places sheep’s wool insulation between two hemp-lime panels. Initial hygrothermal simulations suggested promising performance, prompting full-scale testing with Wool Insulation Wales.

Unlike many plant fibres, sheep’s wool has a microscopic scale structure that repels liquid water while still absorbing and releasing water vapour. This combination complements hemp-lime, which performs well in regulating moisture within the building envelope. Together, the materials may create a durable, moisture-managing insulation system.

To validate the simulations, the research team constructed a full-scale test wall near Neath, Port Talbot. Equipped with temperature, humidity and heat flux sensors, the structure was monitored for three months under exposed weather conditions. According to the researchers, the measured performance exceeded the simulated results, although longer-term monitoring is still required.

Bridging Research and Industry

A key aspect of the project is collaboration with industry partners. According to Dr Latif, combining academic research with practical expertise helps align laboratory testing with commercial requirements such as cost, standards, constructability and public acceptance.

Although the early results demonstrate practical potential, several challenges remain. Long-term performance data for bio-based building materials is still limited, particularly regarding durability, moisture behaviour and fire performance under recognised testing standards. Public confidence also depends on transparent performance data that validates these systems over extended periods.

Current follow-up research is investigating shredded Welsh sheep’s wool both as a standalone insulation material and as part of hemp-lime composite systems. Future work will also examine replacing mineral binders with bio-based alternatives, further reducing the environmental impact of building envelope materials.

Source & photos: Cardiff University