Weaving Welsh wool into the future of sustainable building design

Impact Acceleration Account (IAA) funding has allowed Dr Eshrar Latif to realise his work on bio-based building materials beyond simulations.

Synonymous with rolling Welsh hills and ancient prosperity, sheep are firmly woven into the history of Wales.

But for Dr Eshrar Latif, Senior Lecturer at the Welsh School of Architecture, there was an opportunity to build them into the future of sustainable construction.

Motivated by the climate crisis, Dr Latif wants to design buildings that are both environmentally responsible and healthier for their inhabitants. There are two ways of looking at sustainable architecture, he says:

“The first view prioritises carbon minimisation above all else. It tends to reduce operational carbon while paying limited attention to circularity, biodiversity, or end-of-life outcomes.”

Eshrar describes this perspective as “carbon tunnel vision”. He favours "a whole-life perspective” in his research.

“It values low operational and embodied carbon, renewability, and considers multiple environmental indicators,” he says. “In addition to global warming potential, it evaluates ecological and health impacts. I belong to this second, holistic approach.”

Eshrar’s path to sustainable buildings began with a BSc in Architecture at the Bangladesh University of Engineering and Technology.

Motivated by his pursuit of holistic design, Eshrar's Cardiff University master’s degree in Planning Practice and Research helped place sustainability within a wider urban and planning context.

Eshrar turned his focus to bio-based building materials, such as hemp fibre and hemp-lime, through his Innovate UK-funded PhD in Building Physics at the University of East London.

“Because of the need for mitigation of global warming, I became interested in low-carbon buildings and undertook a secondment at the Centre for Alternative Technology (CAT), which was famous for working with sustainable communities in the middle of Wales.”

“I focused on the hygrothermal performance of hemp fibre and tried to characterise it in terms of its high-grade thermal properties. I also investigated how it works with other materials like aerogel or Phase Change Materials.”

What is hemp-lime?

Hemp is a fine, strong, bast fibre obtained from the industrial plant, Cannabis sativa. The hemp fibre comes from the stem of the plant, which has a fibrous, woody core. The hemp fibres are separated from the bark of the stem by the process of defiberisation using specialised equipment. When mixed with lime – a slurry made from limestone – a material called hemp-lime is created, which has incredible sustainable characteristics, Eshrar explains:

“Since its first development in France in the 1980s, hemp-lime has been performing very well. This is because when lime is mixed with hemp, it provides excellent fire protection. It also has high pH levels, giving it anti-mould growth properties. Its high thermal mass is also integral for insulation purposes.

“Lime production usually uses 70% of the carbon that concrete cement production uses, so it naturally embodies less carbon.

“When mixed with hemp shiv, the resulting hemp-lime composite can have a very low, and in some cases potentially negative, carbon footprint. This is because hemp absorbs CO₂ during plant growth, while the lime binder gradually carbonates during curing and use, the calcium hydroxide reacts with atmospheric CO₂ to form calcium carbonate.”

A tried-and-tested material, Dr Latif is now working on different optimisations of the hemp mix. He recently shared his work as a keynote speaker at the International Hemp Building Symposium 2025, in Minnesota, USA.

Eshrar began a partnership with Wellspring, a sustainable-living company based in South Wales, who wanted to improve the materials used in their housing developments.

After developing five different hemp-lime mixes, they were monitored on absorption, moisture buffer, and moisture-dependent thermal conductivity, and suggestions were made for future wall panels – insulation materials enveloped in hemp-lime.

Since working with Wellspring, and concerned with the decline of the Welsh sheep wool industry, Eshrar was determined to see if other envelope suggestions could work by using sheep wool as a bio-insulator.

“I developed a different envelope system by putting sheep wool in between two hemp-lime panels. We did lots of simulations, and they worked quite well.

“If you look at sheep wool under a microscope, like human hair, it has scales like roof tiles. Those scales help repel liquid water at the fibre surface, while still allowing the fibre to absorb and release moisture vapour. That combination is very unique.

“Other plant-based fibres don't work very well with liquid. But when hemp-lime is mixed as a whole material, this composite is good at absorbing water. So I thought if we mixed these two materials, it would be a durable system.”

“The most rewarding aspects of my work are being at the forefront of research on low-carbon and healthy building materials, knowing that my work opens new pathways to reduce global warming, and seeing industry adopt the findings through collaboration.”

— Dr Eshrar Latif

After carrying out successful simulations, Eshrar made collaborating with industry a priority.

To scale up his use of Welsh sheep’s wool, he combined academic research with industrial application to establish a longer-term innovation pipeline with industry partners.

“Researchers may prioritise building physics questions, while industry counterparts focus on application, cost, standards, and public perception. Collaboration aligns these perspectives, improves study design, and accelerates validation in real projects,” says Eshrar.

“It is also a two-way knowledge exchange: partners gain robust performance evidence, and the research benefits from access to sites, data, and feedback that make the findings more relevant and scalable.”

To test the wool system and exchange his research, Dr Latif undertook an industrial placement with Wool Insulation Wales.

“We made a full-scale wall near Neath, Port Talbot, an environment with lots of wind and rain. We built our small test building with a wall of the envelope system and put temperature, humidity, and heat flux sensors inside.

“We monitored the test site for three months, and we found that it was actually performing better than the simulation said. However, we could only test for a few variables, so we still have very limited performance knowledge.”

Yet, the project aligned laboratory testing and numerical simulation with on-site monitoring, demonstrating practical viability and broadening the partnership network.

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One of the project's difficulties is capturing how bio-based materials behave over time in real buildings, as long-term datasets are scarce.

Dr Latif broke it down: “There is still a need to validate models across laboratory tests, hygrothermal simulations, and on-site monitoring, and to generate robust fire performance data for materials and assemblies under relevant standards. Moisture, temperature, and biological activity interact in complex, time-dependent ways”.

Public perception adds a second challenge. There needs to be confidence in durability and fire performance, which Eshrar addresses by producing transparent performance data.

Eshrar has already completed a follow-up collaboration on Welsh sheep’s wool as insulation.

The continued research evaluated the benefits of shredded wool as an insulation material, both on its own and as part of a hemp-lime system.

Priority areas for further research for Dr Latif include the time-dependent durability of biobased materials and the replacement of mineral binders with biobased materials, further intertwining himself with the future of sustainable building design.

Eshrar’s work was made possible with funding from the Impact Acceleration Account (IAA) Industrial Placement (KEPS) grant.

The IAA (KEPS) promotes collaboration, skills development, and technical knowledge transfer through placements and secondments, ensuring that both the scientific and practical sides of a problem are addressed.