This document discusses embodied carbon in building construction. It provides information on sources of embodied carbon at different stages of construction and from different building materials. Concrete accounts for a large portion of global carbon emissions, but using materials like fly ash and slag in concrete can reduce emissions by 40%. Steel is highly recyclable but new steel production relies on non-recycled material. Timber sequesters carbon and cross-laminated timber buildings have lower embodied carbon than equivalent concrete or steel structures, even accounting for sequestration over the building's lifespan. Material choices, structural form, and efficient use of resources all impact a building's whole life carbon emissions.