The built environment is estimated to be responsible for as much as 39% of the global energy-related CO2 emissions. A terrible track record for such a vital industry. But why does the construction industry pollute so much? Among the biggest contributors to the abysmal CO2 emissions of the built environment are construction materials. Cement and steel are the most predominant materials since they are an essential part of the foundations, as well as structural elements, of most buildings. With 4.1 billion tonnes of cement that have been produced in 2020, it is estimated that cement alone contributed as much as 8% to global CO2 emissions. As for steel, it outputs about 2 times as much CO2 as its weight during its production phase. Other materials such as PVC or polystyrene, typically used for plumbing and insulation respectively, also contribute negatively to the total environmental impact of a building. Yet, these materials are commonly found in the majority of today’s buildings, as well as being the go-to for new ones. In the age of anthropogenic climate change, the need for a radical transformation is clear. The built environment needs a shift in practices and habits if the minimal goals for emission cuts are to be met.