The world of Energy Performance Certificates (EPCs) is undergoing a significant transformation with the introduction of the Home Energy Model. This new calculation methodology aims to address longstanding criticisms of EPCs and the Standard Assessment Procedure (SAP). At City Science, we’re not only closely following these developments but also actively contributing to the evolution of EPCs through our Innovate UK-funded Advanced EPC project. Let’s dive into the key differences between the Home Energy Model and SAP, and explore what these changes mean for the future of energy efficiency in existing buildings.
From Worksheets to Python: A Digital Revolution
One of the most substantial changes is the shift from pen-and-paper worksheets to a centralised, open-access Python code. This move promises several benefits:
- Faster updates and easier implementation across all providers
- Improved consistency in results
- Greater transparency in the calculation process
However, this transition isn’t without challenges. The technical nature of the new model may create barriers for some industry professionals who are less familiar with coding. To address this, we need better explanations and visualisations of the process, as well as targeted stakeholder engagement to capture insights from experienced practitioners.
Key Changes in the Model
1. Wrappers for Up-to-Date Data
The Home Energy Model introduces “wrappers” – sections of code that apply the latest fuel costs and carbon intensities to energy demand calculations. This addresses a major criticism of SAP, where outdated values could lead to misleading comparisons between different heating systems.
2. Higher Time Resolution
Moving from monthly to half-hourly resolution allows for more accurate modeling of:
- Heat pump efficiency variations
- Weather compensation in heating systems
- Battery and PV system performance
- Time-of-use tariffs
This increased granularity will provide a more realistic picture of a home’s energy performance.
3. Uncoupled Heating Zones
The ability to model different zones within a home independently is a significant change from SAP’s whole-house approach. While this allows for more nuanced modelling of temperature differences between rooms, it also raises questions about how to calculate and compare overall heat loss rates.
The Advanced EPC Project: Pushing the Boundaries
At City Science, we’re not just observers of these changes – we’re actively working to shape the future of EPCs through our Innovate UK-funded Advanced EPC project. Our approach combines four key elements:
- Improved EPC Survey System: We’re developing a more accurate understanding of property energy performance, including the measurement of key performance metrics.
- Realistic and Flexible Calculations: By incorporating the Home Energy Model and allowing for more user input, we aim to account for factors like occupant behaviour.
- More Useful Metrics: We’re creating outputs that help people better understand their property’s energy efficiency and potential for improvement.
- Clear Upgrade Recommendations: Our goal is to provide more accurate assessments of the impact of various energy-saving measures.
The Advanced EPC project has two main goals:
- Prepare a white paper for the UK Government, recommending EPC improvements based on our home monitoring insights and use of the Home Energy Model.
- Develop the Advanced EPC into a commercial offering, integrating it with our wider retrofit modelling and recommendations tools.
The Future of EPCs
As the Home Energy Model continues to evolve, we anticipate several exciting developments:
- More informative and dynamic EPC wrappers
- Potential for interactive EPCs that allow homeowners to explore different scenarios
- Better reflection of installation quality and real-world performance
- Integration of measurement data to improve accuracy
Challenges and Opportunities
While the Home Energy Model represents a significant step forward, there are still areas that need attention:
- Reflecting Quality: We need mechanisms to account for the quality of installations and building components, addressing the performance gap between design and real-world energy demand.
- Measuring Performance: Incorporating actual measurements (e.g., heat transfer coefficient, air tightness, U-values) into the EPC process could significantly improve accuracy.
- Simplification for Existing Buildings: The development of an RdSAP equivalent for the Home Energy Model will be crucial for assessing older properties efficiently.
Looking Ahead
The combination of the Home Energy Model and innovative research projects like our Advanced EPC marks a new era for energy performance assessment. These developments promise more accurate, dynamic, and useful evaluations of building energy performance. As we at City Science continue to work on projects related to measuring and modelling building performance, we’re excited about the potential for these changes to drive more effective retrofits and accelerate the transition to low-carbon homes.
The journey towards more accurate and useful EPCs is ongoing, and we look forward to sharing more insights as our Advanced EPC project progresses. Sign up to our newsletter for updates as we continue to explore and shape the future of building energy assessments.