Lime-hemp (chaux-chanvre) insulating render

Natural hydraulic lime (NHL) + hemp shiv (chenevotte) applied as a breathable insulating render coat to existing masonry, roughly 4-6cm for thermal correction, 8-10cm for real insulation, sprayed or hand-applied, with a lambda around 0.07-0.12 W/m.K and a ~100-year life well applied. Distinct from hempcrete infill (same materials, but a monolithic structural infill cast in a frame): this is the render/coating form used to insulate and finish old walls in renovation, respecting the existing structure. Vapour-permeable; excels in felt comfort and humidity regulation more than in raw R-value.

Cost
Low-medium
Upkeep
Occasional
Skill to build
Intermediate
Lifespan
~100 years when well-dosed, thick enough, and correctly applied.
Embodied carbon
Low
Space / material use
Medium
Output timing
None
Skill to repair
Basic
Regulation (FR example)
Changing the external appearance of an existing building normally requires a prior declaration (declaration prealable) at the mairie; stricter rules and an architect consultation apply within a protected or heritage perimeter.

Note: Cost, carbon and footprint are rated against the other options for this same need, not in absolute terms.

What your site needs

Existing masonry wall to coat (renovation context); slow even drying needed after application.

Inputs

none

Outputs

none

Sources

Tutorials

What this page does not tell you

No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.