Embodied carbon ("Building material production") is really insignificant compared to other emissions. It is not worth adding cost to densification to drive these numbers down – concrete and steel are nothing compared to the energy required to heat/cool suburban houses and fuel cars to access them.
study: not only do apartments reduce emissions through improved energy efficiency and better travel patterns, they also have significantly less embodied carbon per resident than low density housing because they use building materials more efficiently www.sciencedirect.com/science/arti...