The Reduced Data Standard Assessment Procedure (RdSAP) is the approved methodology used in the UK for assessing the energy performance of existing dwellings. RdSAP relies heavily on default values and data gathered by Domestic Energy Assessors (DEAs) during onsite visits. DEAs use the method to produce the Energy Performance Certificates (EPC). An EPC rates a property’s energy efficiency on a scale of A-G, with A being very efficient and G being inefficient.
Full SAP Calculations on the other hand are used to produce energy related documents for new homes. These usually are required by building control authorities in order to examine compliance of a new build with latest building regulations. Part of these documents is an EPC.
In January 2023, The Times published an article calling EPCs a “national scandal”. While A and B ratings tend to slightly underestimate actual energy use, EPCs have a reputation for overestimating consumption and emissions for less efficient homes. The Times stated that this makes the certificates “misleading,” making it difficult to set accurate baseline targets for improvements. Energy experts agreed that EPC inaccuracy warrants significant reforms. Some even claimed the certificates provide little practical value.
New SAP Assessments Methodology
In August 2023, the Building Research Establishment (BRE) released details regarding RdSAP10, the first major update in the reduced version of the SAP calculation methodology. Industry professionals highlighted some key changes:
• DEAs must manually measure all windows instead of relying on defaults based on age of construction
• Additional measurements are introduced to account for different construction types
• Heat pumps are now more frequently recommended as an energy efficiency upgrade given the government’s net zero carbon priorities
The aim is that the extra data will produce assessments better reflecting the unique attributes of each dwelling. But will these reforms resolve longstanding issues around misleading EPCs?
Why The New SAP Assessments Will Not Resolve Misleading EPC Concerns
Many within the domestic energy assessment community have expressed doubts over whether the introduction of RdSAP10 and its expanded data requirements will address EPC accuracy issues.
When EPCs launched in 2007, DEA training involved comprehensive classroom learning followed by field training in real-world domestic environments. This allowed trainees to build practical expertise around critical concepts like building materials, insulation, heating systems, and metering.
In recent years, most courses have switched to condensed 3-day online formats. Candidates from any background can now gain DEA certification after submitting just five assessed energy reports, with training fees under £1,000.
Without hands-on experience, critics argue, these rapid online courses leave dangerous knowledge gaps, especially for entrants without construction experience. Assessors may lack understanding of wall types, insulation materials, and heating systems. Some cannot distinguish between single and dual electric meter tariffs or LED light types. Most have never encountered a heat pump first-hand. Is it reasonable to expect them to produce accurate diagnostics and provide tailored improvement recommendations?
Handing a more comprehensive assessment tool to insufficiently trained assessors risks further degrading EPC credibility. While a more advanced calculation method represents technical progress, without better training, energy performance ratings and upgrade advice seem likely to remain “scandalous” in the eyes of many landlords and homeowners.
To uphold EPC integrity, the government and accreditation bodies should focus on screening DEA candidates based on relevant expertise while mandating comprehensive qualification programmes suited to trainee backgrounds. It seems equally “scandalous” to accept entrants from wholly unrelated fields into condensed online courses and expect them to grasp advanced building performance concepts.
By persisting on training new Domestic Energy Assessors, of unrelated backgrounds, with 3-day online courses, inaccurate certificates will continue undermining public faith.
