Retrofitting existing buildings for sustainability is crucial for reducing environmental impact, enhancing economic benefits, and improving social well-being. Existing buildings contribute significantly to global energy consumption and carbon emissions, making retrofitting a key strategy for mitigating these effects. However, the process faces challenges such as technical, financial, regulatory, and logistical obstacles. Integrating new technologies with outdated systems is complex, and high initial costs and uncertain returns on investment pose financial barriers. Regulatory issues, including building codes and zoning laws, complicate retrofitting efforts, while disruptions to occupants add operational difficulties. Innovations in sustainable retrofitting offer promising solutions. Energy-efficient technologies like advanced HVAC systems, high-performance insulation, and energy-efficient lighting reduce energy consumption. Renewable energy integration, such as solar panels, wind turbines, and geothermal systems, enhances sustainability. Smart building technologies, including automation systems and IoT sensors, enable precise energy management. Sustainable materials and practices, such as green roofs and recycled materials, contribute to overall sustainability. Successful case studies demonstrate the feasibility and benefits of retrofitting, showing significant economic and environmental gains in historical, commercial, and residential buildings. Future trends include advancements in retrofitting technologies, increased regulatory support, and the growing market for green building certifications. Public-private partnerships present opportunities for collaborative efforts in promoting sustainable retrofitting. Despite challenges, continuous innovation and investment are crucial for overcoming obstacles and achieving a sustainable built environment. Stakeholders must actively engage in and support retrofitting initiatives to realize long-term environmental, economic, and social benefits.Retrofitting existing buildings for sustainability is crucial for reducing environmental impact, enhancing economic benefits, and improving social well-being. Existing buildings contribute significantly to global energy consumption and carbon emissions, making retrofitting a key strategy for mitigating these effects. However, the process faces challenges such as technical, financial, regulatory, and logistical obstacles. Integrating new technologies with outdated systems is complex, and high initial costs and uncertain returns on investment pose financial barriers. Regulatory issues, including building codes and zoning laws, complicate retrofitting efforts, while disruptions to occupants add operational difficulties. Innovations in sustainable retrofitting offer promising solutions. Energy-efficient technologies like advanced HVAC systems, high-performance insulation, and energy-efficient lighting reduce energy consumption. Renewable energy integration, such as solar panels, wind turbines, and geothermal systems, enhances sustainability. Smart building technologies, including automation systems and IoT sensors, enable precise energy management. Sustainable materials and practices, such as green roofs and recycled materials, contribute to overall sustainability. Successful case studies demonstrate the feasibility and benefits of retrofitting, showing significant economic and environmental gains in historical, commercial, and residential buildings. Future trends include advancements in retrofitting technologies, increased regulatory support, and the growing market for green building certifications. Public-private partnerships present opportunities for collaborative efforts in promoting sustainable retrofitting. Despite challenges, continuous innovation and investment are crucial for overcoming obstacles and achieving a sustainable built environment. Stakeholders must actively engage in and support retrofitting initiatives to realize long-term environmental, economic, and social benefits.