<p>This research defines the characteristics for the development of an archetype model that represents a two storey, detached, single family construction built according to the 2006 Ontario Building Code. This is utilised as the basis for an investigation to continue the research on the existing Toronto housing stock to meet Passive House certification. Retrofit strategies of different levels were developed for the walls, roof, floors, mechanical ventilation, air tightness and heating and cooling equipment. Utilizing BEopt, a multi-objective simulation program, cost optimal configurations of retrofits were determined. The results were simulated in WUFI Passive to determine viable solutions for PHIUS compliance for the lowest life cycle cost. The results demonstrated that for the modern archetype, an average life cycle cost of $91,124, can reduce the archetype's energy use by 59% to meet the PHIUS certification requirements.</p>