Adaptive reuse contributes to giving buildings a new life by employing them in appropriate uses that ensure that they continue to play an effective role for society and enhance their value to protect them against future encroachments or negligence. The study focuses on the concepts of adaptive reuse and their impact when applied to valuable buildings, where the essence of the process lies in achieving integration between the requirements of preserving the values of heritage buildings and the sustainability requirements to adapt them and prolong their survival cycle، It is necessary to qualitatively study all the measures used in each field and determine the appropriate type of function of the building to accommodate new requirements without losing the elements of value and authenticity. The research adopts an inductive approach in studying the adaptive reuse of heritage buildings and determining the sustainable design requirements of existing buildings to determine the controls of the sustainable adaptive reuse process for those buildings. Then following the comparative analytical approach in studying two experiments of this type of projects  in the United States of America (the Adobe SF601 building in San Francisco and the Ecotrust building in Portland), To identify how adaptive reuse can be successfully and strive to obtain accreditation from such sustainable design assesments as LEED-BREEAM and to achieve a balance between both things that may conflict in some aspects.the research ends with the extraction of the most important methods and strategies of intervention in those cases with an assessment of the efficiency of used methodologies.