Carbon negative.
Breathes like
a living wall.
Hempcrete is not a new material. It has been used in construction across Europe for three decades. Wales has the crop, the lime geology, and the construction sector to become a leader in it. What it has lacked is the domestic supply chain to make it viable at scale.
Beth yw e · What It Is
Hemp hurd.
Lime binder.
Water.
Hempcrete is a composite of hemp hurd — the woody inner core of the hemp stalk — mixed with a lime-based binder and water. The mixture is cast into moulds or sprayed onto a structural frame to form walls, floors, and roof insulation.
It is not a structural material in the load-bearing sense — it requires a timber or steel frame. But as an infill and insulation material it outperforms conventional alternatives on almost every metric: thermal mass, vapour permeability, acoustic performance, and embodied carbon.
The lime binder continues to absorb CO₂ as it cures — meaning hempcrete walls become more carbon-negative over time, not less. A well-built hempcrete wall will continue sequestering carbon for decades after construction is complete.
Perfformiad · Performance
Carbon Negative
Sequesters more CO₂ than is emitted in its production and installation. The lime binder continues absorbing carbon after construction.
Breathable Wall
Vapour-permeable construction regulates internal humidity naturally, reducing condensation and eliminating the need for mechanical ventilation in many applications.
50-Year Lifespan
Hempcrete walls harden and strengthen over time as the lime binder carbonates. Buildings constructed in France in the 1990s show no material degradation.
No Cement
Lime binder replaces Portland cement entirely. Cement production accounts for approximately 8% of global CO₂ emissions. Hempcrete eliminates that input from the wall build.
Local Material
Grown and processed in Wales. Lime is abundant in Welsh geology. The material supply chain can be almost entirely domestic — reducing embodied transport emissions to near zero.
Thermal Mass
High thermal mass moderates temperature fluctuation, reducing heating and cooling loads. Particularly effective in the Welsh climate of mild but variable temperatures.
Cynsail · Precedent
Four houses built
in Iowa.
Wales is next.
Iowa — Hemp Block Houses, 2024
Hemp Cymru's Strategic Adviser, Sonia Klein, spent three years and $1.6 million developing a novel, patented process for creating hemp block — a prefabricated hempcrete unit that installs like a conventional masonry block but performs like a living wall system.
Four houses were completed in Iowa in 2024. The technology is now being licensed internationally. Hemp Cymru expects the first Welsh licensee to be a farmer's co-operative in Pembrokeshire — using hemp grown in Wales, processed in Wales, and built into Welsh homes.
The construction application is not a distant aspiration. The material science is proven, the process is patented, and the supply chain architecture is being built now.