Toward Net-Zero Renovations: Integrating Building Simulation and LCA for Whole-Life Carbon Assessment

Enhancing the energy efficiency of buildings often necessitates additional
materials and advanced technologies, many of which are not locally sourced. This can
result in embodied greenhouse gas (GHG) emissions that may offset the savings from
reduced operational emissions over the building's lifetime. Consequently, embodied
emissions play a critical role in whole-life GHG emissions reduction and must be evaluated
alongside operational emissions to meet emission reduction goals. This study explores the
integration of life cycle impact assessment (LCIA) with building performance simulation
(BPS) to assess the whole-life GHG emissions of residential renovation strategies. An
archetype representing a post-World War II single-family dwelling in Belgium serves as a
case study for evaluating six retrofit scenarios. These scenarios combine different envelope
interventions and materials (petrochemical-based and bio-based options) with varied
energy systems and storage technologies, aiming for low-energy and ultra-low energy
performance levels. By coupling LCIA with BPS, the analysis captures both embodied and
operational GHG emissions over the building’s lifecycle and illustrates the trade-offs
involved in material and design choices. The dynamic BPS approach also accounts for
projected changes in the electricity mix and energy demand patterns. Findings show that
deep energy retrofits can lower total GHG emissions by up to 70% compared to the
unrenovated baseline, achieving a minimum of 11.7 kgCO₂e/(m²·y). Despite this
improvement, none of the scenarios satisfy the Danish threshold of 8.2 kgCO₂e/(m²·y) for
total GHG emissions. Sensitivity analysis reveals that factors such as heat pump efficiency,
building airtightness, and photovoltaic panels efficiency significantly affect results. The use
of bio-based insulation materials achieves up to 7% lower embodied emissions compared
to synthetic alternatives. This research presents an integrated framework for balancing
operational and embodied emissions, delivering practical guidance for practitioners and
policymakers aiming to meet European decarbonization targets through sustainable
renovation of the existing building stock.