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Meeting expected energy performance in new homesSeptember 2014

There have at last been positive indicators that the house building industry is recovering from recession. However, the recovery brings a different set of challenges. How to meet the projected demand for more homes than ever? How to address the increasingly complex technologies and systems required to meet the ever increasing Regulatory requirements? How to ensure that the new homes delight owners not just on day one, but continue to do so for many years to come? Not least among this jigsaw puzzle of pieces is the issue of delivering homes that actually meet the expected energy performance, and more specifically the Zero Carbon Hub’s recommendation to Government in 2011 that by 2020 at least 90% of all new homes meet or perform better than the designed energy/carbon performance. Since making this recommendation the Hub have been working with the housebuilding industry to better understand how this ambition might be realised.

Earlier this year the Zero Carbon Hub released their end of term report (Closing the Gap Between Design and As-Built Performance) on the evidence for a performance gap between the as designed or expected performance, and the as-built performance of homes. In the context of the Hub’s project the as-built performance is taken as the measured performance of the home as constructed, rather than the measured performance with occupants in residence. Their findings highlight problems with skills and knowledge, communications and responsibility for the final energy performance of the dwelling.

Following on from interim reports published in July 2013, Closing the Gap between Design and As-Built Performance this project drew on the experience and expertise of over 160 professionals in the house building industry that identified possible sources and causes of the performance gap. From these ideas the Hub derived a list of over sixty issues that were researched across a wide range of evidence, ranging from technical standards and papers to secret knowledge and ‘anecdotal’ data, which was detailed in their Evidence Review Report released at Ecobuild earlier this year. These were analysed and structured into a matrix based on how well and reliably they were documented, and to what extent they contributed to the performance gap. The Hub team also devised and conducted an end-to-end review of the housebuilding process on over 20 development sites volunteered by housebuilders and an audit of SAP assessments. A testament of the commitment of the industry to the project was the fact that a lot of the evidence gathered and reviewed was not in the public domain and was only made available to the Hub to help inform the findings.

Perhaps the most enlightening element of the work has been the findings from the end-to-end review. This has sought to systematically collect data at each stage of the housebuilding process, starting with concept design, moving through detailed design, procurement and construction. Semi-structure interviews with key members of the project teams were conducted to get an understanding of the design and procurement processes; design information was reviewed for detail and completeness and site inspections were made and documented. These inspections were timed to allow the greatest number of active plots to be reviewed on a development, with early stage plots just coming out of the ground, through to final decorations being completed. Of the twenty developments reviewed, a majority were of large housebuilders but the review also included medium and small regional housebuilders.

From all this evidence the Hub has identified fifteen areas where the industry and government need to work together to develop solutions that will help meet the Hub’s recommendation and 2020 ambition. A further seventeen areas are identified where additional evidence gathering and research is needed to fully understand their impact in the context of the performance gap.

What do these highlighted issues begin to tell us? That we struggle to communicate the intended energy performance for the design from the earliest stages, and that we have ongoing problems with communicating the design intent throughout the detailed design. That we also don’t communicate back from site what is, and what is not buildable. This greatly influences architectural detailing issues and site practices that may have been acceptable 20 years ago, no longer meet the required standards. Finally, that there is nearly a complete absences of engineering rigour around the design and installation of the services for our homes.

To move forward and Make Buildings Better the housebuilding industry needs to engage in understanding what their clients (homeowners, social and private landlords) really want; update its methods of communicating and sharing information and adopt a system of verifying performance that covers the whole process from design to construction. This is echoed in the main recommendations made in the Hub’s End of Term report, which calls for a general increase in the level of knowledge and skills in the industry (referred to as Energy Literacy), more quality control of design, manufacture, construction and verification for energy efficiency and more robust evaluation and procedures for statutory compliance. It is also important that the continual development that is required needs to be supported by reliable testing procedures and dissemination routes that would benefit the entire breadth of the industry.

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