Why The Standard Assessment Procedure for the Energy Rating of Dwellings is Flawed by Poor Assessor Training

26th March 2024

The Reduced Data Standard Assessment Procedure (RdSAP) is the approved methodology used in the UK for calculating the energy performance of existing dwellings. RdSAP relies on default values based on the age of build, and on data gathered by Domestic Energy Assessors (DEAs) during site surveys.

Introduced in the early 2000s, RdSAP paved the way for Energy Performance Certificates (EPCs), which were rolled out in 2007. EPC are now produced by DEAs or SAP Calculation agencies.


EPC rates a property’s energy efficiency on a scale of A to G, with A being excellent and G extremely inefficient. The certificate also estimates potential carbon dioxide emissions.


EPC inaccuracy warrants significant reforms

In January 2023, various UK publications called 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. In particular, 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 to the SAP assessment methodology since its inception. 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 habitable spaces within roofs.
  • 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 Calculation Methodology 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.

Alex Papaconstantinou SAP Agency

Alex Papaconstantinou, founder of nationwide SAP Calculations agency epc4less, argues that without hands-on experience 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 take accurate measurements and provide tailored improvement recommendations?

Handing a more comprehensive assessment tool to insufficiently trained assessors risks further degrading EPC credibility. While RdSAP10 represents technical progress, without better entry and ongoing training, energy performance ratings and upgrade advice seem likely to remain “scandalous” in the eyes of many landlords and homeowners.

Restoring Rigour to DEA Training

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. Police officers, barbers, or baristas often share DEA classes with architects and engineers despite vastly different levels of preparation.

By persisting with a crude “one-size-fits-all” assessment training model, inaccurate certificates will continue undermining public faith while setting up many DEAs to fail in their intentions to positively impact building sustainability.

Instead, tailored learning journeys accounting for applicants’ existing knowledge should become the norm. This starts with candidates demonstrating genuine construction, property or sustainability experience before undergoing rigorous energy assessment training to address any gaps.

Without better matched energy assessor education, the well-meaning aim of upgrading UK housing stock risks being waylaid by a lack of trust in assessor competence and certificate accuracy around critical SAP calculations.