The construction industry accounts for approximately 40% of the global carbon emissions and is the largest consumer of materials and energy. Given the Paris Agreement target towards global net-zero greenhouse gas (GHG) emissions, significant changes are required in the design, construction and use of buildings. This study applies a qualitative approach that combines a systematic literature review (SLR) with in-depth semi-structured interviews with experts to analyse existing carbon neutrality frameworks and decision support tools; expanding current knowledge by bringing to the fore the challenges experienced in implementing these frameworks. This research effort reveals an inadequacy in frameworks for effective decision-making on decarbonisation strategies along the project lifecycle. A novel framework that breaks down the activities and decision points across the entire project lifecycle is proposed to bridge this gap in literature. The developed framework defines whole lifecycle cost, whole lifecycle energy use, exergetic lifecycle and whole lifecycle emissions as the four critical underpinning variables considered in making decarbonisation decisions. It further details the key evaluation criteria to facilitate decision-making at each stage of the project lifecycle and provides decision-makers with contextual guidance for assessing the impact of their decarbonisation decisions at the planning, delivery, closure and operations phases of the project. It will assist academic researchers, building owners and industry professionals to keep track of the project's carbon neutrality target and encourage best practices for carbon emission reduction in the building sector.