Harnessing Heat from Hemp

Hemp-lime concrete, also known as hempcrete, is a combination of three constituents; hemp shiv, lime-based binder and water. The hemp shiv acts as the aggregate within the hemp-lime mix, and its low density provides a lightweight concrete. I suggest that future housing estates are built using hemp-lime to reduce the carbon content, increase thermal insulation thus reducing the energy demand for heating of the building. Hemp-lime can be cast in-situ or used in pre-fabricated panels to form walls.

Experiments into the life cycle assessment of hemp-lime have shown it to be carbon negative. During the growth of the hemp plant, carbon is absorbed and stored throughout its life-time in a process named carbon sequestration. When installed in place as a wall, the lime in the material undergoes carbonation, furthering the amount of carbon in the material. The use of this material can aid the reduction of carbon dioxide in the atmosphere, and minimise the amount of embodied carbon in building materials.

Hemp-lime has an excellent hygrothermal performance; the effectiveness in providing a comfortable internal environment, in terms of thermal comfort and humidity. The material works by having a low thermal conductivity meaning the amount of fabric heat loss from the internal environment to its surroundings is low. In addition, the hygric properties of hemp ensure a comfortable relative humidity of the building as the material takes in moisture to ensure the humidity remains in equilibrium. These two effects reduce the need for heating and mechanical ventilation, and therefore lower the requirement for primary energy usage within buildings.

The use of hemp-lime could help revolutionise the building industry to improve air quality for occupants of the building, reduce the carbon footprint of the building and lower the energy demand. The material cost and construction methods are feasible and not too dissimilar to conventional building materials.