In 2020, the extraction, transport and manufacturing of materials for the building sector accounted for 10 per cent of global greenhouse gas emissions. If buildings are to make meaningful contributions to keeping global temperature rise to 1.5 C above pre-industrial levels, limiting emissions from building materials is crucial. To achieve this objective, engineered versions of age-old building technologies, like wood, straw or bamboo, are critical. These bio-based building materials generally demand less energy in manufacturing and have the ability to capture and store carbon through photosynthesis. This is why experts in green building policy, climate science and architecture increasingly tout the benefits of transforming buildings from a giant source of carbon into a large carbon sink.