Retrospective dynamic life cycle assessment of residential heating and cooling systems in four locations in the United States

Abstract

Heating, ventilation, and air conditioning systems (HVAC) and water heaters are responsible for a relevant portion of the total Greenhouse Gas (GHG) emissions related to the building life cycle. A significant effort will be needed to substantially reduce building-related GHG emissions to meet the increasing demand to meet goals for energy use and GHG emission reduction. This study evaluates the GHG emissions of two alternative residential HVAC systems: natural gas furnace and electric air conditioning, and an electric heat pump, in a typical single-family house located in four different climate zones in the U.S. using a life cycle assessment model that includes spatial variations such as climate and electricity generation mix and temporal variations such as the changes in the generation mix and greenhouse gas emission factors for electricity generation over time. The locations selected are in very cold, cold, marine (temperate), and hot-humid climate zones in the U.S. The reduction in GHG emissions over time occurred due primarily to the changes in the electricity grid mix. As a result, the heat pump system had the greatest reduction in GHG emissions over time and had the lowest GHG emissions over the study period in two of the four locations. If the decarbonization of electricity production continues and refrigerants with low GHG potential are widely used, the heat pump can be the HVAC system with the lowest GHG emissions in all climate zones studied.