French architecture and landscaping firm Lemoal Lemoal has completed a new public building in the small town of Croissy-Beaubourg, east of Paris. Constructed using hempcrete blocks, the Pierre Chevet sports hall is making news for probably being the first carbon-negative building in the world.

Hempcrete, which is made from a mix of hemp hurds, lime and water, is a lightweight bio-composite building material that weighs 6-8 times less than concrete but delivers high thermal, acoustical and structural performance as well as fire resistance (REI 30). Hemp’s carbon sequestering properties are impressive with the plant’s ability to absorb up to 15 tonnes of carbon per hectare; it’s also a fast-growing plant, can be grown with less water in most soil types, and is lighter than wood.

For the 380sqm Pierre Chevet sports hall, the hempcrete blocks were made by cement manufacturer Vicat using hemp cultivated in France and assembled less than 500km from the project site, further reducing the carbon footprint.

According to Lemoal Lemoal, the sports hall’s structure consists of wooden half-vaulted porticoes leaning against a wall of hempcrete blocks for support. The hempcrete walls are clad with cement fibre panels to protect the blocks. The rustic appearance of the hempcrete blocks presented a challenge for the architects when convincing their clients about the material’s viability as an alternative to concrete. The Pierre Chevet sports hall is the first public building in France to be constructed from the hemp-based biomaterial.