The purpose of this study is to analyze the scope of the expected improvement effect of office buildings and educational research facilities according to green remodeling. Thus, in order to quantitatively grasp the architectural performance of the existing buildings, the building thermal performance, the airtightness, the indoor environment, and the air quality were measured using equipment. The analysis indicated that the envelope performance and the indoor environment were unsatisfactory compared to the current legal standards, and for indoor air quality, CO₂ and formaldehyde were measured to be dissatisfactory in some buildings. The energy analysis results indicated that the improvement range differed according to the renovation history for each building, resulting in differences in the energy-saving rate for each alternative. The reduction rates of primary energy consumption using energy simulation were 38.5–67.4% for office buildings and 23.7–66.3% for educational research facilities, and the payback periods were 14 to 27 years for office buildings and 12 to 30 years for educational research facilities. These results are expected to contribute to the activation of green remodeling because they can be used as indicators to predict the expected construction cost, the payback period, and the expected effect required for green remodeling.

In this study, the economic feasibility of green remodeling (GR), which could improve the health, safety, and energy of elderly households considering social cost, was analyzed. As a result, the net present value of GR was ‘−10,267 USD (49.7%)’, which was found to be uneconomical compared to the total construction cost (20,981 USD, 100%) despite benefits of energy saving, carbon reduction, and air pollutant reduction. Based on this result, in order to expand GR for low-income elderly households, who cannot afford to perform GR, a GR support measure linked to the currently implemented energy conversion and old-age housing support policies was proposed. It allows the government to perform GR for low-income elderly households with 1/4 of the total construction cost. This result could revitalize GR to reduce greenhouse gas and contribute to housing stability for low-income elderly households who are vulnerable to COVID-19 and climate change.

The Government of Korea uses green remodeling (GR) as a central policy for achieving carbon neutrality in the building sector. However, despite GR’s energy-saving benefits, it raises embodied carbon (EC) due to the incorporation of new materials, and there is a lack of impact analysis and assessment research. Thus, this study established the GR-LCA methodology to evaluate the environmental impacts (EIs) of GR, including EC. The methodology disaggregated and assessed the effects of EC and energy on GR in terms of GR’s proportion of EC, six EI categories, and the carbon reduction impacts. The analysis revealed that GR’s EC accounted for 10.6%, reducing to 9.89% when EPD materials were used. In terms of the reduction impact across six EIs, GWP was reduced to 0.84 and EP to 0.96. However, ODP, ADP, AP, and POCP, all elevated by high EIs from material inputs, increased to 626.7, 1.04, 1.16, and 250.09, respectively. Ultimately, the carbon reduction in GR was 24.9% when considering only energy usage, and 16.1% when including EC. When EPD materials were applied, the efficiency of reduction improved by an additional 0.6%, indicating a minimal application effect. Based on these findings, the differences in GR’s EC compared to new constructions, reduction limitations, and potential improvements were discussed.