Performance of the building envelope – design versus actual performance

For some time, the government has shown concern regarding the gap between theoretical and actual performance within building projects.
This potential gap occurs as a result of the following:

  • Builders buying cheaper products than what the architects specify
  • Inaccuracy of data relating to performance
  • Inaccuracy with joints in the building envelope; poor insulation
  • Errors in BR443
  • Quality control issues on site

Ultimately, these issues directly affect the buildings energy and carbon performance.

What is Zero Carbon Hub?

Zero Carbon Hub, as a non-profit organisation, work with both the government and industry in order to tackle such issues surrounding climate change. This involves identifying the individual components that cause this gap and implementing the appropriate solutions. By engaging both industry and government, Zero Carbon Hub strive to deliver low and zero carbon homes, their main ambition being to deliver Zero Carbon Homes in England from 2016.

Duncan King, technical manager at Construction Products Association, summarises the “End of Term Report” on Closing the Gap, Design & As Built Performance, which has just been published by the ZCH:

The report provides a clear set of recommendations for both government and industry to address this issue. These recommendations are based on the evidence gathered and the resulting assessment process as documented in the Hub’s earlier “Evidence Review Report” issued in March 2014. A copy of this report can be downloaded from the following link – https://www.zerocarbonhub.org/recent-publications

The solutions in the End of Term Report have been grouped into five key themes which I have provided extracts from below:

  1. Energy Literacy

    Across the whole construction industry there is limited understanding of as-built energy performance and the existence of the performance gap. Thus an urgent need exists in the training of new and existing members across the whole industry. The development of a recognised card scheme is proposed.

  2. Improving Quality Output

    There is a need to create a more robust industry-led approach to construction detailing, linked to improved quality control from design through construction to the commissioning stage. There is a clear need for manufacturers to address many areas of the performance gap, including improved product labelling, design and installation instructions. Procurement teams need to prioritise energy performance when procuring materials and labour. Improved quality control from design through the construction phase is required with rigorous independent commissioning of services.

  3. National Compliance Method and Regime

    Conventions used for calculating SAP input data need to be reviewed and in some cases be linked to qualification schemes to ensure only those with sufficient knowledge provide this service. In addition, the governance of SAP accreditation schemes, assessors and the role of Building Control all need review.

  4. Demonstrating Performance

    There is a need to refine existing diagnostic tests to make them more useful, usable and consistent and to develop new techniques. Also, manufacturers need to adopt testing methods that better reflect the performance of their products as ‘systems’ within actual buildings.

  5. Continuing Evidence Gathering

    Expansion of the current evidence gathering process is required to increase understanding of the performance gap and disseminate findings and feedback to developers, industry and government.

These five themes are greatly expanded in the Detailed Recommendations Summary starting on page 10 of the report.

Next Steps: Priority Actions for Industry

  1. Performance assessment R&D

    Undertake the R&D 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 & knowledge development

    Ensure that as-built energy performance, including learning from ongoing R&D, 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 for Government

  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 g addressed and to demonstrate this by 2020.

  2. Stimulate industry investment

    Signal their long term intention to support the industry in providing the information necessary to quantify the performance gap and create loops required to drive continuous improvement by funding research and development of testing, measurement and assessment techniques with immediate effect.

  3. Strengthen compliance regime

    Take action by 2016 to ensure that the 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, are 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.

Roadmap

The Hub calls for an early statement from Government regarding the 2020 Ambition to be included within the Building Regulations Part L 2016 announcement to include:

  • A commitment to have in place by 2018 an approved process by which industry can submit their methodologies for demonstrating performance
  • This will only be used to gauge performance across the industry and not be used as a method of deciding if a building complies with Part L

Jeremy Dunn, Technical Director at Glazing Vision comments:

“It is important that all construction product manufacturers consider the claims that they make and are in a position to substantiate those claims.
Glazing Vision has made significant investment over the last two years working with Anglia Ruskin University on a Low Carbon KEEP knowledge transfer program.
Completing such programs has allowed us to make huge strides with our thermal modelling and design expertise. Understanding heat loss through our particular range of products has allowed us not only to develop those products making them more efficient, but more importantly it has allowed us the ability to develop a methodology for u-value calculations. This means that we can accurately calculate the overall u-value for any given roof light and back this up with validating data that can be provided to the client.”

To find out more information regarding energy performance and ways of reducing the performance gap when using rooflights, call our technical department on 01379 353 741, or click here to book a CPD.