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Simultaneously reducing building energy consumption and maintaining acceptable indoor CO 2 levels is challenging. This study applies a system-level life cycle assessment to compare two approaches for indoor CO 2 level reduction: increasing the supply airflow rate and direct air capture (DAC) of CO 2 from ventilation for utilization (CCUS) in methanol, carbonated concrete blocks (CCB), and stainless-steel slag construction blocks (SSSB). Greenhouse gas (GHG) emissions and energy demand were compared across energy scenarios to identify optimal emission reduction and energy performance strategies. Results show that buildings with integrated DAC have 51% lower energy consumption than those with the increased airflow rate. At the system level, increased airflow consistently demonstrates the highest energy demand and GHG emissions across all scenarios, whereas CCUS approaches reduce these emissions by 8–31%. The heat source is the key factor determining the most effective emission reduction strategy. For conventional heat supply, replacing steam curing with CO 2 curing in CCB is the most effective approach, whereas SSSB is most effective with low-carbon heat. CCB also provides the greatest energy savings among the analyzed options. Scaling to Finland’s office building stock reveals that the CO 2 utilization potential of construction blocks is constrained by market capacity in CCB and feedstock availability in SSSB. Methanol production, while offering the highest utilization potential, provides only modest emission reduction (9%). Although building-integrated CCUS cannot significantly contribute to Finnish emission targets, it offers crucial co-benefits including energy savings, regulatory advantages, and substitution of emission-intensive products, making it a valuable supplement to industrial CCUS strategies.
Zhaurova et al. (Wed,) studied this question.