Hempcrete Construction

What is Hempcrete?

Hempcrete (also known as hemplime) is a bio-composite material made primarily from the inner woody core of the hemp plant (hemp hurds or shives) mixed with a lime-based binder (such as hydrated or natural hydraulic lime) and water. Unlike conventional concrete, hempcrete is not designed for load-bearing applications; rather, it is used as an insulating infill in timber or steel-framed buildings, providing excellent thermal mass, moisture regulation, and fire resistance.

How Hempcrete is Made

1. Harvesting and Decortication

• Harvesting Hemp:
  Hemp plants are harvested at peak maturity to ensure optimal fiber quality. The plants are then processed to separate the outer bast fibers from the inner woody core.

• Decortication Process:
  The decortication process involves mechanically breaking down the hemp stalks to isolate the hemp hurds (the woody core). This process can be done manually or with specialized machinery. The hurds are then cleaned and prepared for use in the mix.

2. Mixing the Ingredients

• Binder Selection:
  A lime-based binder is selected, typically a blend of hydrated lime (which sets by absorbing CO₂ during carbonation) or natural hydraulic lime. Sometimes, pozzolanic materials or a small amount of cement are added to accelerate setting.

• Proportions and Consistency:
  The hemp hurds are mixed with the lime binder and water in carefully controlled proportions. The exact mix can be adjusted based on the desired density, thermal insulation properties, and application requirements. The resulting mixture is a workable, clay-like material that is easy to apply.

3. Application and Curing

• Casting or In-Situ Application:
  The freshly mixed hempcrete can be cast into formwork to create prefabricated blocks or applied in situ (directly into wall frames). In both cases, the material is tamped or pressed to ensure even density and proper bonding.

• Curing Process:
  As hempcrete cures, it undergoes carbonation—a natural process in which the lime binder reacts with atmospheric CO₂ to harden and develop strength. This process not only solidifies the material but also sequesters carbon, making hempcrete a carbon-negative material over its lifespan.

Construction Applications

Non-Load Bearing Walls & Insulation Panels

• Infill Material:
  Hempcrete is most commonly used as an infill material within a timber or steel-framed structure. Its lightweight, insulating properties help maintain a stable indoor climate by combining thermal mass with excellent insulation.

• Prefabricated Panels:
  In some projects, hempcrete is cast into panels or blocks that can be assembled on site, streamlining the construction process and reducing labor costs.

Finishing Plaster and Wall Treatments

• Exterior and Interior Use:
  Hempcrete can be finished with lime plaster, creating a breathable, durable surface that regulates moisture, reduces mold growth, and provides a natural aesthetic.

• Fire Resistance and Acoustic Benefits:
  Due to its low density and high lime content, hempcrete is naturally fire-resistant and offers excellent sound absorption—ideal for residential and commercial buildings alike.

Sustainability and Environmental Impact

Carbon Sequestration and Low Embodied Energy

• A Carbon-Negative Material:
  Hempcrete absorbs CO₂ during the curing process, effectively locking carbon away for decades. This quality makes it a powerful tool in the fight against climate change.

• Energy Efficiency:
  With lower embodied energy than traditional concrete, hempcrete reduces overall energy consumption during construction. Its natural insulation properties also contribute to long-term energy savings in heating and cooling.

Promoting Sustainable Construction Practices in Namibia

• Local Resource Utilization:
  Hemp is a fast-growing, renewable crop that can be cultivated in various Namibian climates. Using locally grown hemp for construction not only supports sustainable agriculture but also reduces reliance on imported building materials.

• Economic and Community Benefits:
  By adopting hempcrete, Namibian builders can create job opportunities, stimulate local economies, and develop innovative, eco-friendly construction practices that set new standards for the industry.

Get Involved

Join the Hempcrete Movement in Namibia

Advocate for Policy Reform:
Support initiatives aimed at integrating sustainable building materials into national construction standards. Help pave the way for broader adoption of hempcrete and other eco-friendly materials.

Embrace the future of sustainable construction. Join us in harnessing the power of hempcrete to build healthier, more resilient communities and a greener Namibia—one wall, one block, one building at a time.