By Jonathan Platt, existing buildings lead at AES Sustainability
In the years following the Grenfell Tower tragedy, the UK construction and property sectors have undergone a profound regulatory transformation. Fire safety is now a dominant driver when it comes to the design and construction of new buildings – and rightly so. It is also just as important for refurbishment and the driving force behind many façade remediation and recladding projects, with strengthened legislation and oversight placing resident safety at the forefront of decision-making.
However, as the industry mobilises to remove combustible materials and achieve compliance with Part B requirements, there is a growing need to ensure that energy performance is not inadvertently deprioritised. Recladding schemes represent a rare and significant opportunity to improve both safety and sustainability outcomes and realising this potential depends on embedding energy performance assessment into the process from the outset.
Energy modelling and Part L compliance should not be treated as secondary or reactive considerations within fire improvement led projects. Instead, they play a crucial role in ensuring that buildings perform effectively as holistic systems. External wall intervention., such as the removal and replacement of cladding, insulation and associated element, trigger requirements under Part L of the Building Regulations. This means that any affected thermal elements must be assessed against current energy efficiency standards, creating both a regulatory obligation and a strategic opportunity to enhance performance. Where approached correctly, recladding works can deliver meaningful reductions in heat loss, improve airtightness and address long-standing deficiencies in the building fabric.
However, achieving these outcomes is not always straightforward. Many of the buildings undergoing remediation are existing high-rise residential assets with inherent constraints, including limited structural capacity, restricted façade depths and complex geometries. In addition, the need to prioritise non-combustible materials in line with fire safety requirements can restrict design choices and complicate thermal optimisation. As a result, full compliance with current Part L standards is not always technically or financially feasible in every instance. This makes a robust, evidence-based approach to energy assessment essential, enabling design teams to demonstrate that reasonable improvements have been made while maintaining the primacy of life safety.
A critical factor in achieving this balance is early-stage integration. When energy performance is considered from the beginning of a recladding project, alongside fire safety, design teams are better equipped to develop coordinated and efficient solutions. Early energy modelling allows different façade build-ups, insulation strategies and material options to be tested before specifications are fixed. This provides the opportunity to optimise U-values, identify and mitigate thermal bridging and ensure continuity of insulation and airtightness layers. It also supports more effective coordination between disciplines, reducing the risk of conflicts or compromises emerging later in the design process.
The importance of this integrated approach is clearly demonstrated by AES Sustainability’s work on a high-rise residential building in London. As part of a major fire safety remediation programme, AES Sustainability was appointed to provide Part L assessments and improvement recommendations to support approval by the Building Safety Regulator. The project involved the removal of existing rainscreen and stone cladding systems, along with combustible insulation and timber elements and their replacement with non-combustible alternatives including Rockpanel cladding, aluminium components and mineral wool insulation. These measures significantly enhanced the fire performance of the building, addressing critical safety risks.
At the same time, the façade interventions triggered the need for comprehensive energy assessment. The building comprised multiple external wall types, each requiring detailed analysis to confirm compliance or identify opportunities for improvement. By undertaking elemental U-value calculations, assessing condensation risk and providing guidance on maintaining airtightness continuity and mitigating thermal bridging, a strategy to meet Part L requirements has been achieved. This level of technical analysis ensured that the thermal performance of the replacement constructions was fully understood and optimised wherever practicable.
In cases where full compliance with Part L could not be achieved due to structural, dimensional, or design constraints, robust feasibility justifications were submitted in line with regulatory guidance. These justifications demonstrated that the proposed solutions represented the best achievable outcome within the project’s parameters, ensuring that improvements were delivered wherever possible without compromising fire safety objectives. The resulting Part L report formed a key component of the submission to the Building Safety Regulator, supporting the successful approval of the scheme and enabling works to proceed with a clear, agreed specification.
This example highlights the critical role that energy performance assessments play not only in achieving compliance, but in supporting effective decision-making within complex, constraint-driven projects. It also illustrates the importance of collaboration between clients, design teams and specialist consultants in navigating an increasingly rigorous regulatory environment.
As the Building Safety Regulator introduces greater scrutiny through the gateway approval process, the need for clear, evidence-based submissions has become more important than ever. Beyond compliance, the integration of energy performance considerations into recladding works delivers significant long-term benefits. Improved thermal performance reduces energy demand, contributing to lower operational carbon emissions and supporting the UK’s broader net zero ambitions. For residents, this translates into improved comfort, reduced energy bills and healthier living environments, outcomes that are particularly important in high-rise residential buildings. From an asset perspective, enhanced energy performance can improve ratings, reduce lifecycle costs, and strengthen overall value in a market increasingly shaped by ESG considerations.
Ultimately, the post-Grenfell landscape demands a more holistic approach to building performance. While fire safety must remain the overriding priority, it should not be pursued in isolation. Recladding projects offer a unique opportunity to address multiple aspects of building performance in a single intervention and failing to integrate energy considerations risks missing that opportunity for decades to come. By embedding energy modelling and Part L assessments from the outset, the industry can ensure that buildings are not only safer, but also more efficient, resilient, and sustainable.
It is possible to demonstrates that this balance is both achievable and essential. Through early engagement, rigorous analysis and close collaboration, it is possible to deliver outcomes that satisfy regulatory requirements while enhancing long-term performance. As the sector continues to respond to evolving regulations and increasing expectations, the integration of fire safety and energy performance will remain a defining challenge, and a critical opportunity, for the built environment.