What are the potential benefits of adopting an intelligent measured data-led approach to retrofit?

This section sets out the range of potential benefits we might expect to see from wider adoption of the approach tested in this pilot project. It considers environmental, social and economic outcomes, all of which will need to be validated once the recommended retrofit works have been completed.

A full explanation of all the outcomes identified, including more detailed and technical commentary and any relevant limitations surrounding these findings, can be found in the Appendices.^m

Environmental benefits

Clearly, the primary long-term purpose of retrofit is to support net zero goals. The pilot project's findings suggest that a measurement-based approach can improve the scoping and costing of retrofit works for energy efficiency, thus enabling housing associations to achieve their net zero targets more easily. This project has also demonstrated that environmental outcomes can be balanced against other priorities when adopting such an approach. The technology used in this pilot allows different principles to guide retrofit simulations based on user preference, meaning the environmental benefits achieved will depend on how these priorities are set.

Reduced operational carbon emissions

Analysis for the 'Core Priority' property group shows that a measured, technology-enabled approach to retrofit could deliver average annual CO₂ savings of around 0.97 tonnes per property.ⁿ This is broadly in line with results from a typical modelled approach to retrofit, which estimates that upgrading a home from an EPC D to a C reduces operational emissions by one tonne of CO₂ per year.²³

Reduced embodied emissions

Importantly, a measurement-based approach also offers potential reductions in embodied carbon emissions – for example, by right-sizing heat pumps to 5kW where appropriate, rather than defaulting to oversized 10kW units. Given that smaller heating units have a lower level of embodied carbon than larger units, this measured data could enable a meaningful reduction in embodied carbon if rolled out across a wider portfolio.

_{^{m See ‘Appendix 7: Potential Outcomes’ in The Science Behind the Insights, for further details.
n These figures have been calculated by Senze’s model for the ‘Core Priority’ group of properties only, using unit costs from the Green Buildings Tool, with the homes measured against their current performance. We do not have a counterfactual to assess against (i.e. the expected reduction in carbon emissions that could have been achieved if a typical modelled approach to retrofit had been used), therefore assessment is framed against the properties’ baseline level of performance.}}

Outcomes vs trade-offs

A key consideration for any future deployment of this technology is the inherent trade-offs between environmental, social and economic outcomes.

As per the current policy framework, measured EPC C compliance was used as the guiding principle for identifying the most effective works in this pilot. However, because EPC ratings are based on running costs, gas boilers (which benefit from a cheaper unit price) can be recommended by the model as the lowest-cost route to EPC C, even though this comes at the expense of greater carbon reduction.

Retrofit programmes could alternatively be modelled around different priorities, including EPC compliance, carbon reduction, energy bill savings, or payback period. If carbon reduction were prioritised as the guiding principle, the recommended interventions would clearly differ significantly, delivering greater emissions savings. Yet this would need to be balanced against other important factors, for example this prioritisation apporach could result in higher upfront costs for housing associations, or risk of greater disruption to residents.

This flexibility is a clear strength of the approach, but it also illustrates the unavoidable trade-offs that must be managed by housing associations when balancing environmental, social and economic objectives.

Social benefits

There are significant potential social benefits for residents from adopting a measured approach to scoping and delivering a retrofit programme. These include:

Increased affordability for residents, leading to reduced fuel poverty

Achieved through more targeted tackling of inefficient homes, greater ability to identify instances of fuel poverty, and contributing to improved home efficiency based on effective interventions.

Senze's analysis estimates that implementing its recommendations could lead to average annual energy bill savings of £715 per property (for the 'Core Priority' group of properties only, using unit costs from the Green Buildings Tool, measured against their current performance).

We would note, however, that this figure should be treated with caution. There is a risk, particularly in the social housing sector, that even if the thermal efficiency of properties is improved, residents struggling to afford bills may continue to under-consume energy, limiting cost-savings. This has been observed in other studies²⁴, while a recent government evaluation of Whole House Retrofit and the Social Housing Decarbonisation Fund (SHDF) found some residents reported no reductions in bills following retrofit delivered under SHDF.²⁵

Improved wellbeing and long-term health

Achieved through more targeted interventions to improve home comfort, for example:

Targeting retrofit works and resident engagement at properties where measured data reveals living conditions that pose risks to wellbeing and long-term health (e.g. very low indoor temperatures or high humidity). This is also relevant in the context of Awaab's Law.
Not over-insulating properties where the measured data shows that their thermal performance is better than expected (the 'Compliance priority' group), noting that over-insulation of homes can lead to issues such as moisture buildup and mould growth, reducing natural airflow, leading to poor indoor air quality and potential health problems.
Targeting retrofit works at properties where the measured data shows that their thermal performance is worse than expected (the 'Home health priority' group).
Targeting interventions to improve ventilation and insulation, which have been shown to be associated with improved respiratory outcomes, quality of life and mental health for residents.²⁶Housing associations could choose to actively prioritise long-term health through using the measured data in combination with accepted guidance on healthy living environments (e.g. guidance from the World Health Organisation or Public Health England) to identify and guide their decision-making.

Economic benefits

It is worth noting that the potential economic benefits outlined below arise from calculations based on a small sample of properties. Further research is required to substantiate the findings. Also, there were several limitations identified in relation to the analysis, which must be considered. These included, for example:

Difficulties obtaining independent costings data for retrofit interventions, noting that this was eventually resolved using data provided by CFP's Green Buildings Tool.
Substantial differences in the stated unit costs and planned spending between Bromford and Flagship in their original retrofit programmes as a result of a fundamental difference in approach. This has a significant impact on the scale of cost-savings that could be realised.
The sample of properties that could be included in the cost comparison was smaller than the full pilot sample. This was due to the need to ensure a meaningful counterfactual was available between properties at the same stage of retrofit.

Further detail is available on the challenges and limitations encountered in relation to the cost comparison, and the pilot project in general, in the Appendices.⁰

⁰'See 'Appendix 9: Challenges and Limitations' and 'Appendix 10: Cost Comparison Methodology' in The Science Behind the Insight for further details.

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What are the main barriers to adopting measured data approaches in your organisation? (Select up to 2)

Uncertain where to start
Upfront cost
Procurement complexity
Resident engagement/consent
Skills/capacity
Uncertainty about benefits
Data privacy/security concerns
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Making use of the measured data and implementing the platform's recommended retrofit interventions could generate significant cost savings for Bromford Flagship.^pThe potential drivers are outlined for each of the identified property groups below.

Group 1: Core Priority (59% of pilot sample)

For the 'Core priority' group, it is estimated that following the measured data recommendations could lead to an average saving of over £12,500 per property relative to pre-pilot cost estimates, based on Bromford Flagship's stated unit costs (calculated based on 27 properties with comparable cost data). This outcome is achieved through targeted interventions tailored to the specific needs of each property, rather than generally applying a blanket fabric-first approach, which can lead to unnecessary measures.

There are also further potential cost savings to consider which could be realised based on a more commercial approach to procurement. While commercial retrofits can achieve cost-efficiencies through economies of scale, residential retrofits are often fragmented and costly to carry out.²⁷ In particular, housing associations are often required to rely on subcontracting arrangements, layering on additional management and procurement costs.

This was observed even within the confines of this project, where wide variation in cost figures was reported by the two housing associations involved. To date, Bromford has generally undertaken a deep, turnkey, whole house retrofit approach at a relatively higher cost, appointing a main contractor to provide an end-to-end package. In contrast, Flagship has generally adopted a package of smaller, more incremental measures at lower cost, delivering large elements of the process internally.

To account for this, we therefore ran a second cost comparison, using unit cost data provided by the CFP's Green Buildings Tool, as a wholly independent source (see Figure 7: Core priority potential cost savings on the next page). This enables insight into the full potential cost-savings that could be realised if procuring retrofit services in a more commercial manner, as well as carrying out more targeted retrofit interventions, as facilitated by an intelligent measured data approach. Factoring in both of these elements, the analysis identified potential cost savings of over £27,500 per property compared with Bromford Flagship's original budget, based on the Green Buildings Tool's independent unit costs.

^p^{All figures stated relate to total cost of interventions, i.e. not just the portion covered by the housing association (under WH:SHF, where applications are approved, up to 50% of costs can be covered by government grant with the remaining costs covered by the housing association).}

CFP's Green Buildings Tool costs

The investment figures used in this report are derived from the CFP's Green Buildings Tool (GBT). These figures are based on a comprehensive library of sources collated over multiple years, combining actual contractor quotes with desk research. Costs include both materials and labour, but exclude VAT. The figures are reviewed and externally validated annually, with the most recent validation completed in July 2025. It is important to note that actual costs will depend on the details of each specific home and can differ from situation to situation.

While it is beyond the scope of this pilot to explore in detail, this is an area that warrants further research given the implications for public funding frameworks and housing associations' procurement.

Figure 7 shows the breakdown of these potential savings for the average property in this group. Note that the estimated savings account for the £1,500 cost of deploying the intelligent measured data approach.

Figure 7: Core priority potential cost savings

Group 2: Compliance Priority (7% of pilot sample)

In this category, it is estimated that making use of measured data could generate cost-savings of around £41,000 per property vs what Bromford Flagship planned to spend through its traditional approach using modelled data (based on four properties for which there is meaningful cost-comparison data).

This is generated through not carrying out any retrofit works to these properties, since the measured data shows that they are already performing as an EPC C equivalent or better.

Based on this data, housing associations may choose to deploy more targeted retrofit works on these properties, pending potential policy changes that would allow 'measured data' to inform EPC ratings (noting the consultation is due to release its decision in 2026). If that happens, these properties could become EPC C compliant based on the data collected for this project, meaning no interventions would be required.

Group 3: Home Health Priority (13% of pilot sample)

Among the Home Health Priority group, there is a risk that retrofit resources have not yet delivered the expected improvements within Bromford Flagship's existing programme of retrofit works.

A portion of homes within the 'Home health' priority group have either already been retrofitted, or are in the process of undergoing retrofit works, yet continue to perform below the level of an EPC C based on measured data. For the nine properties where this is the case, an average of around £27,000 has been spent per property to date.

This implies that expenditure has not delivered the intended performance gains and additional expenditure would be required to deliver the expected improvement to the properties' measured performance, notwithstanding their modelled EPC C rating.^qHowever, we are unable to provide a cost comparison for these properties against Senze's recommended interventions based on the properties' measured data because underperformance cannot be resolved solely by adding additional energy-saving measures.

These underperformance issues may stem from mis-specified fabric or systems, and could require further investigation, upgrades, workmanship checks, or even removal and replacement to address the underlying performance issues.

These findings have potentially significant implications, including for residents who must live in under-performing homes:

Installation quality vs intervention choice – if underperformance is due to poor installation, a measured approach does not provide differentiation. However, if the cause is inappropriate interventions (e.g. unnecessary insulation or efficiency measures in place of fabric improvements), a measurement-led approach could prevent such costs by targeting works based on actual thermal performance.
Traditional approaches to retrofit – the results raise questions about the effectiveness of traditional retrofit approaches and the extent to which they can reliably deliver the intended performance improvements.
Monitoring value – results highlight the role monitoring technology can play in post-occupancy evaluation, providing evidence of whether interventions deliver the intended improvements.

^qNote that baseline performance data is unavailable, so improvements from retrofit cannot be confirmed. However, measured data shows performance remains below EPC C, indicating insufficient progress to date despite investment.

Group 4: No Retrofit Required (21% of pilot sample)

There are no significant economic benefits to be realised for this group of properties, as measured data shows that retrofit is not required based on measured EPC C as the target threshold. Nonetheless, measurement still provides a valuable role in determining whether properties that are rated EPC C or higher sit in Group 3 (Home health priority) or Group 4 (No retrofit needed).

Overall, analysis across the four groups suggests that investing in technology to generate measured rather than modelled performance data can prove cost-effective, with potential savings outweighing the cost of deployment in the majority of cases. This is in addition to the potential environmental and social benefits which could be realised through deployment of this type of technology.

As noted at the outset, there are several limitations related to the analysis that must be considered. Foremost among those is the substantial differences observed in the stated unit costs and planned spending between Bromford and Flagship in their original retrofit programmes, which clearly has an impact on any potential cost-savings. These differences in costs stemmed from a fundamental difference in approach between the two organisations – whereas Bromford has typically undertaken a deep, turnkey, whole house approach to retrofit, Flagship has undertaken more incremental measures at a lower cost.

When assessing just Flagship's properties in the 'Core priority' group, the scale of savings was significantly reduced, although the data did still show that the technology has the potential to generate cost-savings across both Bromford and Flagship properties. Further commentary on the differences observed and the implications of these findings can be found in The Science Behind the Insights.^r

_{^rSee 'Appendix 7: Potential Outcomes' in The Science Behind the Insight for further details.}