气候变化是目前最受关注的全球问题，其对脆弱的自然环境造成了严重负面影响，包括沿海土地和海洋生态系统. 城市对气候变化贡献重大，仅占用全球3%的土地，但造成了超过75%的碳排放。作为城市的主要组成部分，建筑部门的温室气体排放占总排放量的30％，能源消耗占总能源消耗量的40％. 斯里兰卡的建筑部门消耗了超过50%的建材和35%的能源，其能源消耗和环境污染不可忽视，因此需要实施可持续的建筑和城市发展战略。考虑到低效的建筑能源系统和几何形状设计是当前问题出现的主要原因，将现有建筑改造成绿色节能建筑对于创建可持续城市至关重要. 此外，斯里兰卡特别是康提的能源和环境危机的也迫切需要可持续的城市战略作为解决方案. 然而，斯里兰卡等发展中国家受多种因素影响，如节能减碳意识不足、对成本效益关系理解不到位、政府对能效改造措施激励不足等，尚未大力推行建筑节能改造。为了消除这一误解，本文旨在建立一个全面分析框架，以指导利益相关者为斯里兰卡商业建筑确定最佳的节能改造技术组合。本研究使用DesignBuilder软件模拟建筑能源消耗情况，分析加强保温、使用遮阳、高性能窗户、节能照明等措施的技术特征，并通过生命周期分析、能耗情况评估、考虑碳税和未来能源价格的成本效益分析，确定考虑环境影响和经济性能的最佳改造方案。在能耗分析时，节能率被用于衡量每种节能改造策略的效果。在成本效益评估时，使用了净现值（NPV）和投资回收期（IPP）指标评估节能改造措施的直接和间接经济收益。此外，本研究通过OneClick LCA 软件进行生命周期评估，评估了建筑改造的环境改善效益，包括的碳足迹和环境影响指标（GWP、酸化、臭氧层消耗和非生物资源消耗）。本研究各项参数进行了全民评估和敏感性分析。研究结果显示，最佳的建筑改造策略可以将总能耗减少约26.79%，其回收期约为17.33年，碳足迹和上述环境指标的影响（GWP、酸化、臭氧层消耗和非生物资源消耗）分别减少了25%、23%、22%、25%和15%。研究结果发现LED照明对建筑物的能源消耗、成本效益和环境影响的影响最为显著，而建筑围护结构改造也能实现7%左右的节能效果并会带来相当大的环境改善效果, ，但其中平屋顶加强保温并不经济可行. 研究还表明，在温暖湿润和温暖干燥气候条件下，保温措施的节能效果不如其他气候条件。本文为构建可持续性综合分析框架提供了理论和实践支持，可供未来相关研究提供参考.

The most discussing issue in the world right now is Climate change due to the significant negative impact it has caused to extremely delicate natural resources including as coastal land and marine ecosystems. Moreover, the resilience, structure, and function of ecosystems have all generally declined as a result of climate change, along with the changing of seasonal timing as well.in addition to other effects climate change that are relatively irreversible, such as the retreat of glaziers and the thawing of permafrost. World cities contribute significantly to Climate change, but only 3% of Earth‘s land is used for over 75% of carbon emissions. The building sector, the leading dimension of cities, accounts for 30% of global greenhouse gas emissions, 40% of energy consumption, 25% of water, and 40% of resources. Sri Lanka‘s building sector, responsible for over half of construction materials and 35% of national energy, significantly contributes to energy consumption and environmental pollution, necessitating a sustainable city approach. Inefficient building energy design and geometry contribute to this issue.so therefore, converting existing buildings into energy-efficient green ones through energy retrofitting is crucial for creating a sustainable city. And the urgent problem of Sri Lanka’s energy and environmental crisis, particularly in Kandy, calls for a sustainable city approach. However, developing countries like Sri Lanka are reluctant to adopt energy-efficient retrofitting solutions due to several factors, including a lack of awareness, misconceptions about the costs that outweigh the benefits during the building‘s life cycle and the lack of support from governments to encouraging the energy-efficient retrofitting concept in built environment mainly due to its misconceptions. To dispel this misconception about energy-efficient retrofitting, this paper aims to establish a comprehensive analysis framework to guide stakeholders in setting an optimal technical combination of energy-efficient retrofit measures for a selected commercial building in Sri Lanka. DesignBuilder software is used to simulate energy performance by analyzing technical features like insulation, shading, glazing, lighting and renewables. The optimal configuration for assessing its environmental and economic impact is determined through energy performance assessment, life cycle analysis and cost-benefit analysis integrating with carbon taxing and future energy price scenarios. Energy saving ratio is used to execute the building energy performance assessment while assess each EER strategies’ energy efficiency and comparing with baseline building. Regarding the cost-benefit assessment, it used to assess the benefits of EER measures by focusing on direct and indirect financial benefits. The analysis used Net Present Value (NPV), Investment Payback Period (IPP) indexes. Moreover, by LCA it focused on emphasizing the positive environmental impact of retrofitting building through a comparison with baseline building model. OneClick LCA software is used to assess this analysis. Carbon footprint and environmental impact indicators (GWP, Acidification, Ozone depletion, and Abiotic depletion) of both baseline and retrofitted buildings are considered.in addition, these input parameters are thoroughly evaluated and then subjected to sensitivity analysis to determine their impact on the building’s retrofitting performance. This study reveals that the optimal retrofitting of buildings could reduce total energy consumption by around 26.79%, and their payback period was around 17.33 years. Moreover, by retrofitting selected existing building by optimal retrofitting strategies, whole carbon footprint and mentioned environmental indicators impact (GWP, Acidification, Ozone depletion, and Abiotic depletion) reduced by 25%,23%,22%,25% and 15% respectively. Furthermore, this study also emphasizes that, LED lighting has the highest impact on energy efficiency, cost-effectiveness, and environmental impact on the building, while retrofitting the building envelope also brings considerable environmental impact and around 7% energy saving. But flat roof insulation was not viable as much as other passive retrofitting strategies. Furthermore, this study demonstrates that insulation is less efficient in Warm-Humid and Warm-Dry environments than in other area types. This framework for sustainable-comprehensive analysis provides theoretical and practical support which can serve as a reference for future studies on different scenarios.