Using concrete as the primary construction material leaves a huge carbon footprint, which is why building green should focus on minimizing the use of it. Hempitecture is a firm, which is striving to create more awareness for one such green alternative, namely hempcrete, which is concrete made of hemp. However, since industrial hemp is still illegal in the US, hempcrete has to be imported, which raises the price of this building option.
Hempcrete uses the inner woody core of the hemp stalk to make a mineral matrix, which forms a non-toxic, carbon-negative, and energy-efficient building material. Hempcrete is easy to make, since it only requires the core fiber of the industrial hemp plant, a mixture of natural minerals, and water. The resultant hempcrete is completely non-toxic, carbon-negative, and energy-efficient, which makes it one of the most sustainable construction materials available today. The wall system made of hempcrete is also very breathable, has great natural insulating ability and is easy to work with.
Hempcrete is also continually absorbing CO2 during the curing process, since the lime used to make it needs CO2 to completely solidify. A breathable lime-based render is used as the finish for Hempcrete. In the event that wood cladding is used in the construction process, there must be space left for the air to continue to interact with the hempcrete wall, which allows for the material to continue to absorb CO2.
Hempcrete is a very versatile building material, and can easily be used as infill in a traditional stick frame building, especially since hempcrete is also very lightweight. While it may be more expensive to use hemp as a building material in the US, due to the higher cost of importing it, energy savings over time do offset that cost, provided the house itself is designed to be sustainable.
Hempitecture is currently in the process of raising funds for the construction of the first non-residential building made of hemp in the US. The house is to be built in Idaho Base Camp (IBC), and they are currently raising funds via Kickstarter to cover the costs of building with hempcrete. One of the main reasons for this project is to use hempcrete to build a non-private residence, since all such buildings in the US are private residences, meaning that people cannot see and experience for themselves the benefits of using hemp as a construction material.