Assessing embodied and operational carbon of residential HVAC systems: Baselines for life-cycle sustainability

• Embodied carbon emission analysis of 4 HVAC layouts over 20 single-family houses. • Floor heating systems show 15 % less embodied carbon than radiator systems. • Low-GWP refrigerants can make heat pump systems the best in embodied carbon. • Embodied emissions can reach 20 % of overall GWP of HVAC systems. • Results provide baseline for life-cycle GWP calculations in the residential sector. Embodied carbon in residential heating, ventilation, and cooling (HVAC) systems is a dimension of sustainable building practices that is often overlooked in Life Cycle Assessments (LCA). This study focuses on the embodied carbon emissions of four different HVAC systems – air-to-water heat pumps with floor heating or radiators, condensing gas boilers with radiators, and pellet boilers with radiators – in 20 single-family houses. The research aims to provide a comparative analysis that highlights the significance of embodied carbon emissions, supporting life cycle calculation baselines. The paper investigated the material inventory of the different layouts and both embodied and operational carbon emission of the 80 concepts. The results reveal that floor heating systems have a 15 % lower embodied carbon footprint compared to radiator systems. Specifically, floor heating systems have an average embodied carbon emission of 0.464 kgCO 2 eq./m²/year, while radiator systems have 0.548 kgCO 2 eq./m²/year. When including heat producers, gas condensing boiler systems show the lowest embodied carbon with 0.742 kgCO 2 eq./m²/year, while pellet boiler systems exhibit the highest with 1.325 kgCO 2 eq./m²/year. Heat pump systems with R32 refrigerant have 0.972 kgCO 2 eq./m²/year embodied carbon in case of floor heating systems and 1.055 kgCO 2 eq./m²/year in case of radiator systems. Transitioning to low carbon refrigerants like R290 can significantly reduce carbon emissions related to heat pump leakage, lowering the embodied carbon to 0.636 kgCO 2 eq./m²/year and 0.719 kgCO 2 eq./m²/year, respectively, making heat pump systems the most appealing for embodied carbon emissions. Our findings provide vital data for policymakers aiming to align with the EU's ambitious climate neutrality goals, supporting the development of more comprehensive and effective environmental regulations.