As cities expand and research on sustainable housing intensifies, Life Cycle Assessment (LCA) is increasingly applied to evaluate the environmental performance of buildings. Yet, most studies focus on specific design elements or individual components, often missing the broader question: which residential typology provides the most environmentally efficient accommodation—both in terms of space provision and number of occupants housed?
This study fills that gap by assessing four common residential typologies in New Zealand—apartments, townhouses, two-storey and single-storey detached houses—through LCA of embodied Global Warming Potential (GWP). A dual-functional unit approach is applied—gross floor area (GFA) and number of occupants—enabling a dual evaluation: construction efficiency (per area) and accommodation efficiency (per occupant). Environmental impacts are disaggregated by major building systems (substructure, shell, etc.) and materials.
Results show that apartment buildings exhibit the highest embodied GWP per GFA—up to 185% and 107% more than detached houses and townhouses, respectively—due to their increased structural requirements and excessive use of steel and concrete. However, when assessed per occupant, their higher occupancy density mitigates this difference significantly. Furthermore, the positive contributions—biogenic carbon and Module D—were found to be more effective in detached houses, with impact compensation up to 42% of their total embodied carbon, due to less structural requirements and therefore excessive use of timber. This amount was found to be 16% for apartments and 20% for townhouses.
The study suggests that while high-rise buildings are often promoted for their land-use and operational efficiency, their embodied emissions are significant. Furthermore, occupancy density is highlighted as a key factor for future efficient urban development. Further research on typology performance is needed, specifically aimed at assessing the distinct functions of residential buildings—space provision and accommodation—and advancing novel typologies that achieve better balance across both.