Tackling the performance gap between design intent and actual outcomes of new low/zero carbon housing

Panel: 5A. Cutting the energy use of buildings: Projects and technologies

This is a peer-reviewed paper.

Authors:
Rajat Gupta, Oxford Brookes University, United Kingdom
Matt Gregg, Oxford Brookes University, United Kingdom
Rohini Cherian, Oxford Brookes University, United Kingdom

Abstract

The UK Government has set ambitious targets for incremental changes to building regulatory standards, which are intended to achieve ‘zero’ carbon new housing from 2016 onwards. Despite this driver, many of the low carbon solutions are at present untested, creating a gap between ‘as-built’ performance and ‘design intent’. Such a performance gap has the potential to undermine the zero carbon housing policy.

This paper explores the available evidence on the existence and underlying nature of the performance gap and makes proposals on how the problem could be addressed. The paper investigates forensically the discrepancy between ‘as designed’ and ‘as built’ performance of a range of new exemplar low carbon housing procured by public housing providers and private developers in England, UK. These developments include all kinds of built forms (terraced, detached and semi-detached) and modern construction systems (masonry brick and block, timber frame and lightweight steel frame construction with pre insulated panels). Sponsored by the UK Government’s Technology Strategy Board, systematic building performance evaluation (BPE) studies of these low carbon housing developments are undertaken by the authors during post construction and initial occupancy stages.

The performance of the building fabric and service systems are evaluated through a detailed review of design and construction specifications and processes, thermographic surveys, co-heating tests to determine actual heat loss, observation of handover processes and mapping of occupant satisfaction. This reveals unintended fabric losses, installation and commissioning issues associated with low carbon technologies, lack of proper sequencing of building works, and complexity of control interfaces. To ensure that the desired performance is achieved, feedback loops need to be established using a soft landings based approach for better briefing, design, graduated handover and performance in use.