An alternative mass housing topology based on Toronto duplexes. Two families have a set of customized prefabricated living spaces in which they plug into a concrete amenities core that houses a serviceable central location for hydro, HVAC, and core facilities such as kitchens and bathrooms. The system is designed to become more efficient as more units are built, as the units share an off site location that supplies central geothermal and waste treatment facilities that can be integrated and zoned into lane-way spaces within Toronto neighbourhoods. This provides additional economic incentives as excess and additional geothermal energy can be sold back to the neighbourhood to generate revenue to maintain and expand the system. With the unit’s simple structure and prefabricated design, each unit has the possibility to increase in densities to mid-rise apartment occupation levels.