Eric Roberts, Business Development Manager, IES
What is NABERS?
NABERS – the National Australian Built Environment Rating System – is a six-star rating system that measures the energy use of buildings over the course of a year. It has been used in Australia for the past two decades and is now mandatory there for all new buildings over 2000 square metres and buildings that are up for sale or lease.
NABERS UK was launched in late November and is a certification scheme (initially applying to UK commercial office space) which uses the tried and trusted methodology. The methodology used in Australia for the last 20 years has achieved impressive results over that time – 90% of buildings meeting their agreed energy targets, and a 33% reduction in energy usage over all buildings certified.
The NABERS rating scheme measures the operational performance of the building. This is a significant change for the UK which is more used to using Energy Performance Certificates (EPCs) as a target and measure of building energy performance. However, EPCs are based upon predicted or designed performance rather than the measured. This will see a long overdue shift of focus towards energy monitoring and management, away from our current “design for compliance” culture to one of “design for performance”.
What is the process?
The NABERS UK scheme follows a five step Design for Performance (DfP) approach.
The approach is recognised by and complements several other leading industry initiatives, including: the BCO Guide to Specification, BSRIA Soft Landings, GLA Be Seen Energy Monitoring Guidance, GRESB, London Energy Transformation Initiative, RIBA Climate Challenge and the UK Green Building Council Net Zero Carbon Definition.
What do I need to do to get ready?
Detailed modelling of the building and its HVAC systems is fundamental to undertaking this work. This modelling work will also need to be subject to an independent design review and will need to be submitted as required.
The building MUST be accurately modelled with all floors and zones represented along with any shading devices together with the surroundings of the building. So the modeller must have skills in the use of tools such as ModelIT and ApacheSim, from our Virtual Environment (VE) suite, to correctly represent the building geometry so it accurately reflects the form, along with all of the necessary inputs relating to fabric, occupancy, lighting & equipment.
The HVAC system serving the building must be modelled in detail. The NABERS UK guide to Design for Performance states the following:
“The HVAC plant and system input to the simulation program must be an accurate representation of intended operation. This includes the specified number, capacity and configuration of plant and equipment – including but not limited to chillers, boilers, cooling towers, pumps, air handling units, fan coil units and terminal units.
Note: Default performance curves built into the simulation package for part load and low load operation are to be replaced by realistic performance data for the specified equipment.”
In order to be able to meet this requirement the modeller needs to make use of advanced HVAC plant simulation, which can be achieved through the use of ApacheHVAC. This will enable the modeller to model all of the part load performance characteristics of the plant in the design. The modeller will also be able to simulate the control of the plant with far greater accuracy than with other simplified methods, increasing the robustness of results. So in order to undertake any NABERSUK project the modeller needs to have access to ApacheHVAC as well as be fully conversant in its use.
The modeller will need to produce a minimum of six models to meet the DfP requirements, these are:
- The base case model, with the building operating as expected;
- Four off-axis models, being four separate scenarios testing factors that may degrade the performance of the building;
- One combined off-axis model, comprising four off-axis scenarios each of which individually degrades the building performance.
(potential but not limiting scenarios are given within the guidance documents.)
Once the building has been completed and is in operation, quarterly progress reports on energy performance must be submitted to the scheme administrators in order to achieve the certified rating at the end of the first year of operations.
Whilst this is a long way off for schemes at present, thought needs to be given as to the monitoring of the building and more importantly how the data gathered is acted upon to ensure energy performance of the building is subject to continual improvement.
Through the use of our iSCAN platform, real time data from the building can be analysed and used to inform where improvements to operational strategies can be made as well as plant that is operating outside of their optimal performance envelope. The data gathered from iSCAN can easily be compared to the outputs from the simulations performed in the VE and actual vs designed performance easily evaluated. The data gathered can be used to calibrate the model to produce a Digital Twin of the building to allow the testing of more operational strategies and enable the optimum solution to be arrived at, then implemented, helping to improve the NABERS UK rating further.
The accuracy of our advanced HVAC modelling capability, combined with the data integration and analytics capabilities of iSCAN, has been proven to predict simulation results close to reality on countless projects, providing a reliable baseline from which to determine the actual performance of your buildings. This has been achieved, not only in the case of office buildings, but also across many other building use types, including schools, universities, libraries, museums, hospitals, financial services and government buildings.
IES have all of the tools available to enable you to undertake these projects and begin to move into a more performance-based design world. Our software has already been used by our customers on thousands of NABERS certified projects in Australia and New Zealand, such as the 5* rated Aorangi House in Wellington.
Our Consulting team also have many years of combined experience in employing NABERS in Australia and applying the ‘Design for Performance’ approach on projects, making them well equipped to support the NABERS UK scheme. Get in touch with IES Consulting to find out how they can help you on your next project.