This chapter compares the environmental impacts—in the form of direct and embodied emissions and associated land-use impacts—of two opposing US housing types: the low-rise, low-density suburban single family house and mid-rise urban multi-family housing. By isolating and modeling construction assemblies of both conventional and high performance building envelopes for each housing type, our study seeks to illuminate the relationship between new, more materially intensive construction systems and the associated potential lifetime environmental benefits of density. Figure 1 presents a proposed model for residential neighborhood.