Plant & fibre
Hemp-lime (hempcrete)
The woody core of the hemp stalk bound in a lime slurry and cast or sprayed around a frame: a wall that is insulation, moisture buffer, and carbon store at once.
How it behaves
Better-than-zero carbon (the plant absorbed more CO2 than the lime released), vapour-open, mould-resistant, and a fine humidity regulator for composite climates. Non-structural: it wraps a timber frame.
Where it belongs
A revival material: Europe, now piloted in India's hemp belts (Uttarakhand)
In a modern project
Infill walls and roof insulation on timber frames; retrofit linings that let old mass walls keep breathing.