The main measure comes at the concept stage, through the construction system, because structural and main construction materials account for 50 to 70% of a new building's footprint. Low-carbon concretes with low clinker content reduce emissions by 30 to 50% compared with conventional concrete; structural timber and bio-based insulation (hemp, straw, cellulose fibre) are the other alternatives, with bio-based insulation potentially reducing the insulation category's footprint by a factor of 3. Before building, also compare with major renovation, which emits 2 to 4 times less for an equivalent floor area.
Read the source article: A new building's carbon footprint: the RE2020 figures