How could technology be part of the solution?

The potential value lies in enabling programmes to be scoped, designed, and implemented based on measured property-level data rather than modelled data derived from EPC ratings.

Given the challenges in retrofit delivery, digital technology has the potential to play a critical role in scaling retrofit solutions by improving understanding of building energy use, thermal performance, and the targeting of interventions. Its potential value lies in enabling programmes to be scoped, designed, and implemented based on measured property-level data rather than modelled data derived from EPC ratings.

To date, modelled approaches to retrofit have typically been the dominant method used for scoping and delivering retrofit projects in the UK. However, several studies have found that EPCs, and their modelled heat transfer estimates, often provide an inaccurate picture of a building's thermal performance compared with actual measured data.¹⁶This is an emerging area of understanding. However, it has potentially significant implications which could include inaccurate targeting, inefficient use of funds (both public and private), and poor outcomes for residents.

The outline below illustrates the difference between a 'modelled' vs a 'measured' approach.

A 'modelled' approach

A 'modelled' approach to retrofit relies on modelled inputs, generally drawing data from surveys, default values, and standardised calculations to estimate how a building performs now, and how it should perform after retrofit measures are applied. In the UK, EPCs often provide the basis for a modelled approach. EPCs are calculated using the Standard Assessment Procedure (SAP), which estimates a building's energy use based on physical characteristics (such as insulation levels and heating system efficiency) and standardised assumptions about occupancy.

A 'measured' approach

A 'measured approach' to retrofit relies on using actual data from the building to understand its energy use and thermal performance (i.e. the extent to which it allows heat to transfer into or out of the house). It involves physical testing and monitoring, making use of real-time property-level (or even room-level) measurements through sensors and in-use monitoring to identify the most effective, targeted works needed to upgrade the performance of each specific home.

Spotlight on: The Government's EPC Consultation

In December 2024, the UK Government released a consultation to reform the energy performance of buildings regime, with a decision expected in 2026.¹⁷Among the proposed reforms are recommendations relating to the update of EPC metrics, and to refine the requirements for EPCs.

Within the Government's consultation, there is acknowledgement that EPC metrics could make greater use of measured energy consumption and other time-series data. This could potentially include the type of real-time thermal performance data collected for this pilot project.

The Government’s decision in response to this consultation will clearly be significant in terms of the potential implications of this pilot project’s findings.

Given the challenges that exist, digital technology could play a critical role in scaling retrofit by improving understanding of building energy use, thermal performance, and the targeting of interventions.¹⁸

This report seeks to investigate whether this hypothesis plays out in practice – i.e. can technology enable delivery of more targeted retrofit works based on measured data with improved outcomes for reduced cost vs traditional modelled approaches?