The purpose of this study is to investigate absolute environmental sustainability in the built environment, by assessing whether contemporary environmentally optimized approaches to building design, with their associated consumption of resources and subsequent emissions, can be considered within the carrying capacity of Earth Systems. A life cycle assessment (LCA) was conducted for six dwellings to quantify their environmental footprints. Two methods for absolute environmental sustainability assessment were applied to the resulting life cycle inventories; one where the normalisation step applied normalisation factors reflecting carrying capacities of the Earth System and one where characterisation of elementary flows applied characterisation factors based on the Planetary Boundaries. For the assessment of environmental impact of each house in an absolute perspective, different sharing principles were applied to determine the share of the safe operating space that a single-family stand-alone dwelling should be assigned. The study finds that the approaches tested in two of the dwellings, namely reducing the energy consumption and recycling and reusing materials have the greatest potential to reach an absolute sustainable level of impact. The conclusions drawn are found to be dependent of the applied sharing principle used to assign a share of the safe operating space. Nevertheless, as the results indicate that in our current society absolute sustainability for buildings still appear to be out of reach, even with the best attempts at sustainable building design. It is clear that to achieve e.g. lower energy consumption and a cleaner energy mix, action is needed by consumers and politicians alike.