To retrofit or not retrofit: performance data vs modelled EPCs

The research involved a pilot of the Senze targeted retrofit tool by Bromford Flagship, a housing association that owns more than 80,000 homes across east, central and south-west England. Birmingham City University verified the methodology and data outcomes of the report, which was written by The Good Economy.

A total of 121 of Bromford Flagship’s properties were featured in the trial, which tested Senze’s monitoring technology to measure actual thermal performance and compare it with modelled Energy Performance Certificate (EPC) data. The Senze platform then used the real-time property data to suggest which properties to target for retrofit, and the specific interventions likely to be most effective in upgrading the performance of each property to the standard of an EPC C rating, on a granular, room-by-room basis. This service is delivered at a typical cost of £1,500 per property.

According to the report, the pilot’s data “validates the widely shared view that EPCs are often inaccurate in their estimations of thermal performance… Significant discrepancies were observed between individual homes’ modelled EPCs and their measured thermal performance”. The average thermal performance gap was 25%, with 13 properties (11% of the pilot sample) experiencing a level of heat loss that was more than double their modelled predictions.

“This raises important questions about the reliability of EPCs as a decision-making tool for retrofit investment,” the report states.

Senze’s monitoring technology “appears to enable more accurate scoping of retrofit works, avoiding unnecessary interventions against what had been recommended based on a modelled approach using EPC data”, the report adds.

The research team found that the technology-enabled, data-first approach could deliver significant cost savings. More than half (59%) of the properties in the pilot were assessed to require retrofit based on both measured and modelled data. At these properties, the measured data showed that, on average, works could be delivered in a more targeted manner, and at a lower cost to achieve an EPC C rating, than had been planned by Bromford Flagship based on a modelled (EPC) approach. The data suggests that this could lead to an average saving per property of £12,500 for the properties in this group, based purely on the cost of the interventions themselves.

Furthermore, the measured data from Senze suggested that 7% of properties in the pilot sample did not require any interventions to achieve a level of thermal performance equivalent to an EPC C or better, even though they had been earmarked for retrofit, with Bromford Flagship having planned the works and set aside funding. Therefore, were the housing association to deem that the planned interventions were not required, it would save more than £41,000 per home.

Senze’s data also revealed that 13% of the homes with a stated EPC rating of C or better were not performing as such in the real world. The report notes: “Where data was available, Bromford Flagship had already spent an average of £27,000 on retrofit at these properties, yet the measured data demonstrates a risk that these retrofit resources have not delivered the expected improvement in performance as yet. Using the technology to identify this category of properties highlights the risk of ineffective spending based on current methods.”

Social impact is also highlighted as a benefit of the technology-enabled, data-first approach. The report states: “Deployment of this type of technology offers the potential for social impact through targeting properties and retrofit interventions that will be most effective in addressing home comfort issues in addition to improving energy performance. This could include, for example, targeting properties where measured data shows a material risk of damp and mould, and/or ensuring that homes are suitably insulated.

“In addition, interventions can be targeted at properties that would otherwise have fallen out of scope of a typical modelled retrofit programme, but where measured data shows they underperform against their modelled predictions.”

The government has yet to publish its findings following its consultation earlier this year on the reform of the Energy Performance of Buildings framework. The report recommends that the government could allow for a more data-led approach to EPCs and consider how net-zero policy interacts with Awaab’s Law to avoid perverse outcomes.

Lloyds is the largest lender to the UK social housing sector. Chinyelu Oranefo, MD of sustainability advisory, real estate and housing at Lloyds Corporate & Institutional, said: “Notwithstanding the size of the sample, the outputs of this pilot point towards improved outcomes which, if scaled, have potentially positive implications for the optimisation of retrofit, including reduced costs, improved customer experiences and benefits for the environment.

“As you’d expect, this pilot has shown that alongside potential benefits, there are some challenges, unique to the social housing sector, that need to be considered in parallel with any plan to scale an intelligent, measured, data-led approach to retrofit. First, and crucially, data must be collected efficiently and handled responsibly. Liabilities created by hosting measured data need to be clear and possible benefits confirmed: eg could measured data meeting industry standard metrics lead to a presumption that asset managers have fulfilled their regulatory responsibilities? Clarity on points like these will be needed if the sector is to fully embrace the benefits that this pilot indicates prop tech has to offer.”

Bromford Flagship development and asset management innovation lead Michael Craggs added: “While careful consideration is needed to ensure that technology is used appropriately and outcomes are rigorously measured, this pilot underlines the importance of innovation, collaboration and data-led solutions in accelerating progress toward net zero.

“The future vision is to consider how we scale this through a place-based approach. With the continued support of Lloyds and Senze, Bromford Flagship can be sector-leading, being able to build on the pilot’s findings and to fully realise the benefits of data-led retrofit, helping to improve homes, reduce energy use, and support progress toward net zero at scale.”

Read the research in full.

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