Freshwater is in high demand globally, leading to energy-intensive desalination and water transportation systems. Building-integrated greywater reuse systems offer a more sustainable solution. A study compared these systems to conventional ones using Life-Cycle Assessment. Physical and biological treatment techniques produce high-quality greywater for reuse, reducing environmental impact. Guidelines for greywater reuse have been proposed by various countries and building rating systems, supporting its environmental benefits over disposal. This research aims to promote greywater reuse in water-stressed regions like the Middle East and North Africa.