The discrepancy between as-built and as-designed in energy efficient buildings : a rapid review

Energy efficient buildings are viewed as one of the solutions to reduce carbon emissions from the built environment. However, studies worldwide indicate that there is a significant gap between building energy targets (as-designed) and the actual measured building energy consumption (as-built). Several underlying causes for the energy performance gap have been identified at all stages of the building life cycle. Focus is generally on the post-occupancy stage of the building life cycle. However, issues relating to the construction and commissioning stages of the building are a major concern, though not usually researched. There is uncertainty on how to address the as-designed versus as-built gap. The objective of this review article is to identify causes for the energy performance gap in buildings in relation to the post-design and pre-occupancy stages and review proposed solutions. The methodology applied in this research is the rapid review, which is a variant of the systematic literature review method. Findings suggest that causes for discrepancies between as-designed and as-built energy performance during the construction and commissioning stages relate to a lack of knowledge and skills, lack of communication between stakeholders and a lack of accountability for building performance post-occupancy. Recommendations to close this gap during this period include better training, improved communication standards, collaboration, energy evaluations based on post-occupancy performance, transparency of building performance, improved testing and verification and reviewed building standards.