As the built environment sector works collectively towards the goal of zero carbon, eliminating the performance gap between design predictions and the ultimate operational energy performance of our buildings will be key. To support this, project teams need to ensure that they are implementing more accurate modelling throughout the entire building lifecycle – from the design stage, right through into post occupancy evaluations and M&V.
Increasingly, design teams are turning to methodologies such as CIBSE TM54 and CIBSE TM63, together with dynamic simulation modelling and M&V tools and techniques, to deliver improved modelling and operational performance outcomes for their clients. This is particularly being driven by the increasing number of net-zero energy performance targets being set in project briefs, as well as the emergence of more stringent regulatory and voluntary performance standards and industry modelling guidance.
Here we provide a brief overview of CIBSE TM54 and TM63 and the tools, consultancy services and other resources offered by IES to support these methodologies.
What is TM54?
CIBSE TM54 provides guidance to help evaluate and more accurately predict the operational energy use of a building at the design stage. The methodology covers all energy uses - both regulated and unregulated – to provide a more complete and accurate prediction of a building’s expected performance, and can be applied to any building type, whether new or existing.
TM54 recognises that a building’s energy performance depends heavily upon how a building is operated and maintained, not simply how it is designed and constructed. The methodology aims to help engineers deliver on a project brief where an annual operational energy target has been set, by informing the development of the design, controls and operational strategy, as well as allowing them to undertake more accurate calculations of in-use performance, based on the client’s anticipated use of the building and specific operating parameters. This makes it possible to produce more realistic performance targets for the design (versus a traditional compliance modelling approach, which should never be taken as an accurate predictor of operational performance) against which measured performance can be compared.
Within TM54, CIBSE provide guidance on different modelling types, ranging from steady state calculations to dynamic simulation with detailed HVAC modelling. However, the latter approach is widely accepted as providing the greatest degree of accuracy and is most appropriate when dealing with complex buildings or systems, or in cases where contractual performance targets have been set.
TM54 is now recommended by several industry standards and is outlined as a suitable energy forecasting methodology to meet the requirements outlined within Approved Document L2, 2021 for new buildings with a total useful floor area over 1000m2. LETI’s recently launched Operational Modelling Guide also advises that TM54 should be used as the central methodology for energy performance assessments across all building types. There is also crossover with other frameworks and design for performance standards, such as NABERS UK.
What is TM63?
CIBSE TM63 provides a framework for undertaking measurement and verification of in-use building energy performance, to help better understand and identify where performance gaps occur. It forms part of a set alongside three additional TMs (TM61, TM62 & TM64) which deal with various aspects of operational performance. The aim of TM63 is to help designers, contractors, building managers and other relevant stakeholders undertake effective measurement and verification (M&V) of building energy performance in-use.
TM63 is very much seen as being complementary to TM54, since it presents a suitable M&V framework to evaluate the performance predictions and targets set during the design stage once the building enters the operation phase. The approach employs the use of dynamic thermal simulation models, calibrated with actual operational data from the building in-use, to identify any discrepancies in operating conditions or technical faults within the building, versus the design intent.
How can IES support?
Our IESVE software is recommended by CIBSE to undertake the analyses required for a range of CIBSE TMs, including TM54, and can be used in conjunction with our iSCAN platform to facilitate the necessary data collection and calibration process for TM63. Our expert consultancy team also provide a range of modelling services to support these methodologies.
To help make the TM54 process easier, IESVE's ApacheHVAC application also includes UK standard system prototypes and a system design wizard that generates the system and assignments for TM54 models. We also offer a range of specially designed python scripts for TM54, allowing users to undertake:
• Parallel Coordinate Charting
• Parametric Analysis
• Sensitivity Analysis
• Uncertainty Analysis
• Scenario Outcomes
IES's iSCAN data analytics platform further enables designers, contractors and building managers to meet TM63 requirements. Allowing them to analyse the performance of their buildings and leverage M&V capabilities to track and monitor whether expected benefits have been realised. These capabilities make it possible to:
• Automatically uncover hidden inefficiencies, save energy and reduce costs
• Hone in on areas that need attention and tune control strategies
• Design bespoke dashboards around your KPIs and create Command Centres
• Utilise the data performance metrics to create and refine targets
For more information on the technology and consultancy services IES can offer to support these, and other key CIBSE technical memoranda, visit: https://www.iesve.com/cibse-tms