Performance Gap



In recent years, the housebuilding industry and government have grown increasingly concerned over the potential gap between design and as-built energy performance. It could undermine a building's vital role in delivering the national carbon reduction plan, present a reputational risk to the housebuilding industry and damage consumer confidence if energy bills are higher than anticipated.

In response, the Zero Carbon Hub was commissioned to review evidence for the significance of this gap, explore potential reasons for it and set out proposals to address these reasons. They were also asked to identify potential methods for industry to demonstrate progress in achieving the ‘2020 Ambition’.

From 2020, be able to demonstrate that at least 90% of all new homes meet or perform better than the designed energy / carbon performance.


The Project

The project has engaged more than 160 industry experts from across 90 companies, seeking to understand the nature of the Performance Gap and provide solutions. The Zero Carbon Hub team is very grateful for the in-kind support of so many businesses and individuals.  

Initial Phase and Evidence Collection

In the first phase of the project, potential issues leading to a Performance Gap were identified, spanning the entire design and delivery process. These are outlined in the  Interim Progress Report, published in July 2013.

A detailed evidence gathering process was then carried out, including a Housebuilding Process Review method to gather primary evidence from live housebuilding sites. Using this evidence, each of the potential issues were categorised, based on the strength of evidence and the relative impact of each issue. From this, 15 were defined as ‘Priority for Action’ and a further 17 as ‘Priority for Research’, with the remainder as ‘Retain a Watching Brief’.

This revealed widespread evidence of a Performance Gap across all stages of the process of providing new homes. Three cross-cutting themes were identified as primary contributors to the problem: lack of understanding, knowledge and skills; unclear allocation of responsibility; and inadequate communication of information. These findings are set out in the Evidence Review Report, published in March 2014.

Identifying Solutions and the End of Term Report

The final phase of the project focused on generating potential solutions, particularly focused on the ‘Priority for Action’ issues, as well as the cross-cutting themes. Solutions were grouped into five key themes: Energy Literacy, Improving Quality Output, National Compliance Method & Regime, Demonstrating Performance and Continued Evidence Gathering. These are detailed in the End of Term Report, published in July 2014. The Report also proposes several actions for both government and industry, which are critical in closing the Performance Gap:

Priority Actions for Industry

To commit to providing the investment for:

1. PERFORMANCE ASSESSMENT R&D: Undertake the research and development necessary to create innovative testing, measurement and assessment techniques to understand the Performance Gap and develop commercially viable methodologies acceptable across industry for 'demonstrating performance'.

2. SKILLS AND KNOWLEDGE DEVELOPMENT: Ensure that as-built energy performance knowledge, including learning from ongoing research and development, is embedded into training and up-skilling for professionals and operatives.

3. CONSTRUCTION DETAILS SCHEME: Develop an industry owned and maintained Construction Details Scheme providing ‘assured’ as-built energy performance for the most common major fabric junctions and systems.

4. CONTINUED EVIDENCE GATHERING: Support further evidence gathering processes and coordinated feedback to ensure accelerated continual improvement across all sectors of industry.

Priority Actions for Government

To accept the Zero Carbon Hub’s recommendations to:

1. SIGNAL CLEAR DIRECTION: Clearly indicate that, in place of immediate additional regulation, it expects the construction industry to act now and have put in place a number of measures to ensure that the energy Performance Gap is being addressed and to demonstrate this by 2020.

2. STIMULATE INDUSTRY INVESTMENT: Signal their long term intent, by funding research and development into testing, measurement and assessment techniques with immediate effect, to support the industry in providing the information necessary to quantify the Performance Gap and create the learning loops required to drive continuous improvement. Additionally, provide pump prime funding to enable industry to develop a Construction Details Scheme.

3. STRENGTHEN COMPLIANCE REGIME: Take action by 2016 to ensure that the Zero Carbon Hub recommended revisions to energy modelling practices, SAP processes and verification procedures, together with a strong regime to ensure that only suitably qualified persons carry out energy modelling and assessment, can be put in place.

4. SUPPORT SKILLS & KNOWLEDGE DEVELOPMENT: Accelerate the demand for industry developed qualification schemes by requiring energy certified operatives and professionals for developments on public land from 2017.

The Next Steps

Immediate, co-ordinated, pan-industry activity is needed to trigger a cultural shift for as-built performance to become a core element of high quality new housing. A strategically timed series of actions is therefore needed by industry and government between now and 2020, as set out in the Route Map that follows(Click to Enlarge)

Reports and Documents

End of Term Report (July 2014)

Appendix A: Issues List (included in the main report)
Appendix B: Evidence Update (included in the main report)
Appendix C: Design & Assessment Tools Work Group Proposals
Appendix D: Testing Work Group Proposals
Appendix E: Construction Joint Details Work Group Proposals
Appendix F: Assured Performance Work Group Proposals
Appendix G: The Potential Role of BIM
Appendix H: Detail of SAP Sensitivity Analysis

End of Term Summary Report

Evidence Review Report (March 2014)

Interim Progress Report (July 2013)