CARBON-ADJUSTED HOUSING PURCHASE VALUE INDEX: MEASURING THE TRADE-OFF BETWEEN GREEN PREMIUM AND LONG-TERM ENERGY SAVINGS

ABSTRACT Objectives: This study develops a Carbon-Adjusted Housing Purchase Value Index (CAHPVI) to evaluate whether the green premium paid for sustainable residential projects can be justified by long-term energy savings and carbon-related benefits. The paper aims to shift green housing evaluation from a static price comparison to a lifecycle purchase-value perspective. Methods: A composite-index approach was applied to a project-level dataset of 30 urban apartment projects, including 15 green-oriented and 15 conventional benchmark projects. The index integrates six dimensions: green premium, present value of energy savings, present value of carbon benefits, affordability pressure, operating cost, and green evidence disclosure. Indicators were normalized by benefit/cost direction, weighted using the Entropy-CRITIC method, and ranked through TOPSIS. Results: The findings show that green-oriented projects achieved a higher average CAHPVI score than conventional projects, with mean scores of 0.628 and 0.494, respectively. The average green premium was 8.36%, while the mean present value of energy savings reached VND 41.03 million per standardized unit. Energy savings received the highest final weight of 0.246, followed by affordability pressure at 0.224 and green premium at 0.213. Projects with moderate premiums and strong energy-saving evidence ranked highest, whereas high-premium projects with weak sustainability disclosure showed potential greenwashing risk. Conclusion: Sustainable housing value should be assessed through lifecycle financial and environmental benefits rather than upfront price alone. The CAHPVI provides a practical tool for homebuyers, developers, and policymakers to compare residential projects under a carbon adjusted and sustainability-oriented framework.