HPH332 : How accurate are Energy Performance Certificates (EPCs)? – with Tom Gwilliam
May 3, 2023
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Tom Gwilliam, a Sustainability Consultant at Etude, discusses the accuracy and limitations of Energy Performance Certificates (EPCs). They explore the lack of consistency in EPC results, the shortcomings in assessing energy efficiency, and the need for updating outdated assumptions. The chapter also mentions potential future changes in EPCs and emphasizes the importance of accurate ratings in improving existing building stock.
Energy Performance Certificates (EPCs) are often inaccurate and inconsistent, making them unreliable as a measure of a building's energy efficiency.
To improve the accuracy of EPCs, attention should be given to details like thermal bridging and heating system performance, and on-site inspections should be incorporated into assessments.
Deep dives
The Inconsistency of Energy Performance Certificates (EPCs)
Energy performance certificates (EPCs) are meant to provide a rating of a home's energy efficiency and estimated running costs for potential buyers or renters. However, there are several problems with EPCs, particularly in terms of accuracy and consistency. These issues arise from various reasons, including different interpretations and measurements by assessors, reliance on assumptions, and outdated formulas. As a result, EPC ratings often do not align with the actual energy use of buildings. The lack of oversight and standardization further contributes to this disparity. Efforts are being made to update the SAP assessment system, which informs EPC ratings, but changes have been slow. It is advised for individuals interested in purchasing or renting properties to be cautious when relying solely on EPC ratings and to consider obtaining additional information, such as the SAP assessment behind the EPC, to make a more informed decision.
The Role of SAP Assessment in EPC Generation
SAP (Standard Assessment Procedure) assessments are the basis for generating energy performance certificates (EPCs). SAP calculates the energy efficiency of a building by considering factors such as heat loss, domestic hot water usage, and energy associated with lighting, pumps, and fans. The assessments also incorporate assumptions about appliance usage and unregulated energy consumption. However, SAP assessments have limitations, relying on generic assumptions and often missing on-site details. This can result in inconsistencies between different assessments for the same building. To improve accuracy, greater attention should be given to details like thermal bridging and heating system performance. Furthermore, incorporating on-site inspections could enhance the quality of SAP assessments.
Challenges and Opportunities for EPC Improvement
Improving energy performance certificates (EPCs) requires addressing various challenges. One possible solution is adopting the proven quality assurance process of passive house certification, which offers comprehensive assessments of building performance. Additionally, it is crucial to update and revise SAP assessments regularly to reflect modern building practices and technologies. More emphasis should be placed on testing and evaluation of finished buildings to ensure their energy performance aligns with the predicted results. Access to more detailed information about the building, such as heating, ventilation, and occupancy systems, would aid in creating a more accurate assessment. Ultimately, a combination of updated assessments, improved oversight, and providing more transparency to property buyers and renters could enhance the reliability and usefulness of EPCs.
Caution in Reliance on EPC Ratings
Buyers and renters should be cautious when relying solely on energy performance certificate (EPC) ratings as a measure of a building's energy performance. EPC ratings may not necessarily reflect the real energy use of a building, as they rely on generic assumptions and overlook specific factors like thermal bridging and heating system performance. The lack of consistency between assessments conducted by different assessors further compounds the issue. It is advisable to seek additional information, such as the SAP assessment underlying the EPC, to gain a more accurate understanding of a building's energy efficiency. Engaging in discussions with professionals, exploring alternative certification systems like passive house, and considering on-site testing can also contribute to a more informed decision-making process.
Tom Gwilliam explains what Energy Performance Certificates (EPCs) are, how they are created and why they are unlikely to be a useful measure of how energy efficient a building is.
