BREEAM 2018 Could Go Further On the Energy Front to Help Eliminate the Performance Gap

By Edwina Cramp on Friday 17 November 2017

An updated 2018 version of BREEAM New Construction is due to be launched early next year and the BRE recently consulted with industry on the DRAFT manual. IES has reviewed the documents and provided feedback to BRE in particular on the Energy Credit Ene01 and the DRAFT Guidance Note (GN32) which outlines the proposed approach for the detailed energy modelling criteria in Ene01.

Over the years, IES has and still is heavily involved in software development for UK compliance and BREEAM as well as other global rating systems such as LEED. We’ve worked with Green Building Councils all over the world to help create Certification Engines within the IES Virtual Environment (IESVE) that are approved for compliance with relevant rating systems.

However, we feel strongly that in order to tackle the energy performance gap and ensure that energy efficient design intent is followed through into operation, the role and use of virtual simulation tools in conjunction with an integrated design process needs to be more strongly encouraged by the BRE within BREEAM NC 2018.

This includes energy modelling during design of the actual building and not just an NCM compliance model that misses out non-regulated energy use. Non-regulated energy use actually makes up a large proportion of the performance gap – its energy use that designers know the building will have, but which doesn’t need to be accounted for in NCM calculations for compliance and EPCs.

Our main concern is that while the GN32 strategic approach appears to incentivise more detailed energy modelling and reward accurate predictions of energy, there is still an over reliance on NCM methodology and data. We recommend that GN32 eliminates any reference or consideration to ‘default to NCM data’. Giving project design teams the fall back on NCM data will lead to pressure to take the ‘easy option’ that inevitably devalues their analysis and will help to keep the performance gap alive.

The use of UK Compliance calculations for accurate energy assessments has already been widely discredited as not being an accurate prediction of in-use energy. We suggest encouraging designers to move away from the use of compliance calculations towards a more robust analysis method (e.g. ASHRAE 90.1) which could be used to attract (say) twice as many credits, mindful of the fact that BREEAM is always seeking for credits to go beyond the industry ‘norm’.

"We feel strongly that in order to tackle the energy performance gap the role and use of virtual simulation tools in conjunction with an integrated design process needs to be more strongly encouraged by the BRE within BREEAM NC 2018."

Other elements contributing to the performance gap are ad-hoc changes during construction, commissioning errors and lack of understanding by the new owners as to how systems are designed to work. Virtual energy models of the building can and already are being used to help keep buildings on track performance wise from design, through construction, commissioning and handover and on into operation. We feel more needs to be done to ensure that the potential to utilise the energy model during the building’s lifecycle is encouraged and supported.

The post construction stage enables buildings to demonstrate how well they are performing based on real energy data. However, the number of BREEAM credits available at the post occupancy stage is less than rewarded at design for calculations based on UK Compliance. IES recommends that this stage should have at least equal status with pre-construction estimates, the proposed balance of up to nine credits for Energy Performance at design and only four credits for Energy Modelling and Reporting at operation is not reflective of the effort involved. There is also the additional risk that 0 Credits may be awarded where the actual energy performance is worse than the low end of the energy performance range meaning that there is a ‘perceived’ risk by design teams targeting these credits, as they may never be achieved.

The final part of the cycle is taking the energy model on into operation and enhancing it with real-life data during the operational phase, against which you can troubleshoot and fine tune the building, and enable real life data to be more easily incorporated back into the design process. Such models and data can inform either future retrofits of the same building, or the design and construction of other buildings of a similar type.

The GN32 proposal is built toward a single instance of operational energy matching energy prediction, which would involve a large amount of effort into a calibrated energy model but with a small points reward under the BREEAM credit. From experience, the time and expertise investment into this whole process is completely worthwhile for the building and its owners in terms of value, cost, comfort and reducing emissions, but the incentive for a design team to lead this through into the operational stage is minimal. There needs to be a greater appreciation for the overall team responsibility for the workflow to reach a successful conclusion.

BREEAM 2018 is an excellent opportunity to start a dialogue with Dynamic Simulation (DSM) vendors and other expert DSM users to develop a more prescriptive methodology throughout the project lifecycle. For instance, LEED promotes good commissioning, handover and addition of monitoring and measuring system implementation to help move the industry on and facilitate a more integrated approach. This helps to ensure that designers and modellers are not only designing in energy efficiency, but also ensuring the design is built as intended, handed over with relevant information and guidance to owner/occupiers so that it can be operated effectively and achieve the efficiencies intended.

DSM software has advanced significantly in recent years and workflow efficiency tools, through aspects such as parametric modelling should be promoted to drive a systematic series of energy assessments from concept through each project stage. Modelling competence in the UK needs to needs to be developed to use the currently available workflows so that project teams have the expertise available to lead on design feedback.

IES has been helping to raise industry awareness on the Performance Gap through many expert articles as well as through its training and education sessions.

The graph shows studies by Carbon Buzz, Innovate UK and the Carbon Trust which have quantified the magnitude of the Performance Gap in non-domestic buildings. It compares the Building Emission Rate (BER) prediction of building energy performance using NCM methodology to the actual in-use energy consumption.

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Further IES resources on the Performance Gap: