Understanding the Gap between ‘as Designed’ and ‘as Built’ Performance of a New Low Carbon Housing Development in UK

Abstract

This paper investigates forensically the discrepancy between ‘as designed’ and ‘as built’ performance of exemplar low carbon housing in UK, since this performance gap has the potential to undermine zero carbon housing policy. Driven by the UK Government Technology Strategy Board’s Building Performance Evaluation (BPE) competition, a BPE study is undertaken by the authors during post construction and initial occupancy stage of a Code level 5 housing scheme (Swindon, UK) focusing on two house typologies. The performance of the building envelope and service systems are evaluated through a detailed review of design and construction specifications and processes, fabric performance evaluation, observation of handover processes and mapping of occupant satisfaction. This reveals unintended fabric losses, installation and commission issues associated with low carbon technologies, lack of co-ordination and proper sequencing of the building works, and complexity of control interfaces. Lessons from different elements of the BPE study are pointed out and recommendations are drawn for councils, developers, house builders, designers and equipment suppliers to reduce the gap between ‘as designed’ and ‘as built’ performance of future low carbon housing developments.