Whole building energy and life cycle impact modeling was conducted for a single-family detached reference building designed to meet the Passive House Standard. Life cycle operating global warming potential (GWP) and building envelope embodied GWP were assessed for two mechanical system configurations and three Canadian cities. Variations in regional electricity carbon intensity were found to significantly impact both operating and embodied GWP. Embodied GWP was found to be significant relative to operating GWP in locations with access to low carbon electricity. Additionally, use of natural gas mechanical systems in Edmonton resulted in 360% greater operating emissions than in Montreal, while electric heat pump mechanicals yielded 6,600% higher emissions. Finally, the Passive House Standard method for quantifying operating GWP was found to overestimate emissions by up to 3700% in Montreal and underestimate emissions by 34% in Edmonton, when compared to a method accounting for variations in regional electricity carbon intensity.