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Southfield Court: Independent testing confirms Aston Group's retrofit success

Thermal envelope report provides evidence of outstanding building performance.

At Aston Group, we believe the true measure of a successful retrofit project is not when the works are completed, but how the building performs in the years that follow.

23 September 2026

That's why independent post-completion testing is so important. It provides housing providers with confidence that retrofit measures are delivering the outcomes they were designed to achieve, not just in theory, but in practice.

At Southfield Court in Waltham Forest, those results speak for themselves.

Independent assessment validates performance

Before warmer weather conditions made thermal testing impractical, a comprehensive Thermal Envelope Report was undertaken in April 2026 by Stroma Built Environment to assess the performance of Southfield Court following its whole-building retrofit.

Commissioned to evaluate the effectiveness of the fabric improvements and low-carbon heating upgrades, the assessment included:

Smart Heat Transfer Coefficient (HTC) testing over a minimum 21-day period.
Heat 3D U-value measurements of external wall constructions.
Full thermographic surveys of the building envelope.

The findings confirmed that the building is performing exceptionally well from a thermal perspective.

According to Stroma:

“The thermographic survey was conducted to confirm the overall thermal performance of the building. From the thermograms and data collected, it appeared that the building was performing exceptionally thermally, indicating very little in the way of anomalous insulation or areas of weakness. The elevations appeared to be continuous throughout, showing little variation across the surfaces. This is indicative of a very well insulated building.”

The report concluded that the retrofit measures had successfully improved the thermal performance of the building fabric, supporting lower energy demand.

Measuring real-world results

The independent testing found that Southfield Court achieved:

A Heat Loss Parameter (HLP) of 0.6 W/m²K, demonstrating excellent overall fabric performance.
An average measured U-value, including infiltration and ventilation, of 0.5 W/m²K.

External wall U-values of:

Render 0.39 W/m²K
Cladding 0.33 W/m²K

Importantly, the thermographic survey found the building envelope to be performing consistently across the façade, providing confidence that the results achieved were not isolated to individual test areas but representative of the wider building.

A retrofit designed to deliver long-term benefits

Delivered by Aston Group as part of the Social Housing Decarbonisation Fund (SHDF) programme, Southfield Court underwent a comprehensive retrofit designed to improve energy efficiency, reduce carbon emissions and enhance resident comfort.

Alongside extensive fabric improvements, the project included the installation of low-carbon air source heat pump technology, helping to reduce reliance on traditional fossil fuel heating systems.

The independent assessment concluded:

“The measurements and survey carried out have found that the building’s fabric is performing very well following the retrofit. This has complemented the mechanical upgrade to heat pumps and has helped reduce energy consumption, carbon emissions and energy bills.”

Stroma Built Environment

The report concluded that the retrofit measures had successfully improved the thermal performance of the building fabric, supporting lower energy demand.

Creating better homes for residents

Southfield Court is home to vulnerable residents, many of whom have experienced housing instability and homelessness.

Delivering a major retrofit programme within an occupied building required careful planning, close resident engagement and a commitment to minimising disruption throughout the works.

Through Aston Group's resident-first approach, the project was successfully delivered on time and within budget, achieving a resident satisfaction score of 97%.

The latest thermal performance results now provide further reassurance that residents are benefitting from:

Improved thermal comfort
Reduced heat loss
Lower energy consumption
Reduced carbon emissions
More affordable homes to heat.

Building confidence in decarbonisation

As local authorities and housing associations continue to invest in retrofit programmes, there is growing demand for independently verified evidence that projects are delivering meaningful outcomes.

Southfield Court demonstrates how high-quality retrofit delivery, combined with post-completion performance testing, can provide that confidence.

The project has already attracted national recognition as a finalist for both Green Homes Upgrade of the Year - Central and East of England, and Collaboration of the Year - Retrofit projects, at the 2024 Unlock Net Zero Awards.

Southfield Court also welcomed representatives from the Department for Energy Security and Net Zero (DESNZ), who visited the scheme to understand the impact of the programme and hear directly from those involved.

Looking ahead

The Southfield Court Thermal Envelope Report provides clear, independent evidence that the retrofit investment is delivering long-term value.

The testing confirms that the building fabric is supporting the efficiency of the low-carbon heating system and helping to reduce energy consumption, carbon emissions and energy costs.

For Aston Group, this is another example of how successful retrofit projects should be measured, not only by what is installed, but by the lasting benefits they deliver to residents, clients and communities.

As decarbonisation programmes continue to evolve, Aston Group remains committed to delivering retrofit solutions that create measurable outcomes, improve lives and help future-proof the UK's housing stock.

Thermal Imaging Survey

The survey was generally carried out in accordance with the British Standard 13187:1999 Thermal performance of buildings – qualitative detection of thermal irregularities in building envelopes – infrared method.