What Is TM54? Addressing Energy Performance Gaps
Building energy estimations made during the design stage often differ significantly from the actual energy performance observed once the building is operational. This discrepancy is known as the energy performance gap. Performance gaps arise when various factors influencing energy consumption are not fully accounted for in the initial calculations.
TM54, a methodology published by the Chartered Institution of Building Services Engineers (CIBSE), aims to address and mitigate energy performance gaps. It focuses on predicting and evaluating the actual operational energy usage of buildings during the design stage, providing a more realistic estimate of real-world energy consumption.
Common Causes of Energy Performance Gaps
Energy performance gaps occur when there is a discrepancy between the predicted energy use of a building and its actual energy consumption. Common causes include:
- Lack of consideration for buildability & energy implications during early design decisions
- Uncertainty around modelling, numerical values, or dynamic factors like weather, operation & occupant behaviour
- Use of different tools when modelling the same building
- Insufficient construction quality, including changes made after design without a full review of implications
- Incomplete or poor installation, commissioning & handover practices of various systems
- Malfunctioning systems, including inaccurate energy-measuring equipment
- Long-term variability due to occupancy changes, building deterioration & climate conditions
CIBSE TM54 Methodology
While other energy assessment methods, such as SAP (Standard Assessment Procedure) and SBEM (Simplified Building Energy Model), are widely used to meet compliance with Building Regulations Part L, CIBSE TM54 stands out for its focus on predicting actual energy performance.
The CIBSE TM54 guidance is organised into a series of steps that cover the essential elements for carrying out an adequate operational energy performance prediction (TM54 assessment). It underscores the importance of accounting for the many variables influencing energy consumption, including the weather, occupancy patterns, and how systems are operated.
Further guidance includes NABERS Design for Performance. This is a scheme that requires committing to specific performance targets to achieve a designated NABERS energy rating during the design, construction, and commissioning phases of new office developments or major refurbishments.
How Is a TM54 Assessment Conducted?
A TM54 assessment involves creating a detailed energy model of a building during the design stage.
This requires gathering specific information about the building’s design, including architectural plans, mechanical and electric systems, expected occupancy patterns, and other variables. Dynamic Simulation Modelling (DSM) is then used to predict the building’s actual energy consumption.
The final TM54 report documents the predicted energy use and other assumptions, which can be used to identify opportunities for improving the design for greater energy performance. Insights gained from a TM54 assessment can inform design decisions, optimise building operations, and ultimately lead to a more energy-efficient and sustainable building.
Who Can Deliver TM54 Modelling?
TM54 modelling must be carried out by a competent professional with expertise in building energy performance and DSM.
This person must have the necessary skills and a deep understanding of the various elements influencing energy performance in buildings, especially when the most important factors will vary depending on real-world conditions.
Benefits of Operational Energy Calculations TM54
By considering a wide range of operational factors, CIBSE TM54 provides a more accurate prediction of energy consumption compared to other assessment methods that rely solely on theoretical calculations.
For building owners, developers, and occupants alike, this proactive approach to energy efficiency can help to:
- Meet compliance with Building Regulations Part L2A
- Identify opportunities for improved energy efficiency
- Ensure occupant comfort & well-being
- Reduce the carbon footprint of building portfolios
- Demonstrate a commitment to environmental sustainability
- Enhance the marketability & value of assets in the long term
Accredited TM54 Assessments & Reporting from Stroma
Operational Energy Calculations TM54 provides building designers and owners with clear guidance on evaluating operational energy use more comprehensively during the design stage.
At Stroma, we offer a complete TM54 service delivered by Level 5 certified energy assessors - all accredited with Integrated Environmental Solutions (IES) and Low Carbon Consultant approved by CIBSE.
To learn more about how we can support you, explore our Energy Performance Services or get in touch for a quick chat about your requirements. Whether it’s a single property or a full-scale development, we can advise on the best course of action to deliver an effective, overall solution.