Thesis

Mitigating the building energy performance gap : outcome-based policies and the potential for standardization

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T18104
Person Identifier (Local)
  • 202264583
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • Evidence since the mid-1990s has shown a persistent divergence between predicted and measured building energy performance, known as the Energy Performance Gap (EPG). Despite advances in modelling, regulation, and building-performance assessment, the EPG remains unresolved, undermining confidence in sustainable architecture and slowing progress toward zero-carbon buildings. Existing mitigation approaches have largely focused on improving prediction accuracy, while giving less attention to the wider socio-technical, behavioural, operational, and regulatory factors that shape building performance. As a result, the causes and magnitude of the EPG remain inconsistently understood and reported. This thesis aims to critically investigate the EPG as a complex and multifaceted phenomenon. Its objectives are to synthesise evidence on EPG magnitude, identify and evaluate root causes, assess opportunities for mitigation, and develop a more standardised approach to EPG quantification and reporting. A mixed-methods research design was adopted, combining a systematic literature review, root cause analysis, semi-structured interviews, a simulation-based case study using multiple dynamic modelling tools, and a panel discussion. The findings show that the EPG arises from interconnected factors across design, construction, commissioning, and operation. The assessment of NABERS in the UK, an outcome-based rating system originally developed in Australia, indicates that outcome-based approaches can help mitigate design-stage and systemic causes of the EPG by introducing explicit performance targets, post-occupancy evaluation, and stronger accountability. However, their effectiveness depends on sustained implementation and continued operational feedback. The simulation-based case study further demonstrates that reported EPG magnitude is highly sensitive to modelling assumptions and tool selection, with substantial variation occurring even under identical input conditions. This highlights the uncertainty embedded in EPG quantification and shows that model calibration, while valuable, does not by itself ensure predictive validity. The thesis advances a more realistic and accountable understanding of the EPG, supporting improved policy design, more credible performance assessment, and better-informed decision-making. It makes three original contributions to knowledge: first, it provides a comprehensive cross-context synthesis of EPG magnitudes across geographical locations, modelling approaches, and quantification methods; second, it delivers an independent academic assessment of NABERS in the UK; and third, it develops a framework for standardised EPG quantification and reporting that integrates gap definitions and accounts for uncertainty, thereby improving transparency and comparability.
Advisor / supervisor
  • McElroy, Lori Barbara
  • de Wilde, Pieter
Resource Type
DOI
Date Created
  • 2025

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