DELIVERING RETROFIT AT SCALE

Across the UK, local authorities and housing associations are facing growing pressure to improve the

performance of existing homes. Net zero targets, rising energy costs, increased regulatory oversight and a stronger focus on resident health and wellbeing are driving the need for action. Much of the country’s housing stock is also ageing, poorly insulated and often located within conservation or planning sensitive areas, making large-scale retrofit both essential and complex.

The 2024 Autumn Budget saw £1.29 billion committed through the Social Housing Decarbonisation Fund and Warm Homes: Social Housing Fund Wave 3, with a clear objective of lifting social housing to at least EPC Band C.

As projects move from allocation into delivery, attention has understandably turned to PAS 2035 – the national standard that governs domestic retrofit – and what it means in practice when programmes are delivered at estate or portfolio scale.

PREVENTING POOR DESIGN

PAS 2035 emerged in response to the shortcomings of earlier initiatives. Poor design, inadequate installation and limited oversight resulted in underperformance, resident complaints and unintended issues such as

condensation, damp and mould.

In addressing these failures, PAS 2035 established a whole dwelling, fabric-first methodology, supported by

structured risk assessment, defined professional roles and a requirement for post installation review. For complex or high risk retrofit schemes, this level of technical discipline is critical in delivering

safe, durable and effective outcomes.

PAS 2035 is not optional where public funds are involved. Grant funded projects must demonstrate compliance through defined roles including Retrofit Assessor, Coordinator and Designer, and show that proposed measures respond directly to the characteristics and risks of individual homes. For organisations dependent on government funding, alignment with PAS 2035 is both a compliance requirement and a prerequisite for investment.

However, as programmes increase in size and ambition, questions are being raised about

proportionality. Delivering retrofit across mixed tenure, mixed use estates already brings significant logistical and stakeholder challenges. Applying full PAS 2035 processes to hundreds or thousands of dwellings compounds this complexity, particularly in a market where experienced retrofit professionals are in short supply.

PROGRAMME IMPACT

Cost and programme impact are also key considerations. A fully compliant PAS process can include on-site assessments, air tightness testing, borescope investigations, contextual and heritage analysis, energy modelling, design development and ongoing coordination. Each element plays an important role in risk management, but together they are a substantial upfront investment.

For some properties, particularly those with limited scope for improvement due to planning or heritage constraints, this raises legitimate concerns. Where interventions are modest – such as enhanced loft insulation, upgraded heating controls or improved lighting – the cost and time associated with full

PAS compliance can be disproportionate when compared with the value of the measures being installed.

This does not undermine the value of PAS 2035 itself. On large scale or deep retrofit programmes, its

benefits are clear. Schemes involving external wall insulation, low carbon

heat, ventilation upgrades or whole estate decarbonisation rely on robust assessment and coordination to manage technical risk. In these cases, PAS 2035 provides a framework that supports strategic sequencing, improves building performance and delivers tangible benefits in terms of carbon reduction, energy affordability and resident comfort.

The challenge lies in how the framework is applied. A rigid, uniform approach risks absorbing limited funding through process rather than outcomes, particularly where simpler measures

could achieve meaningful improvements quickly. Professional judgement, supported by strong technical leadership, is essential to ensure PAS 2035 remains an enabler rather than a constraint.

DELAYS AND TIGHT DEADLINES

There are also broader delivery risks to consider. PAS aligned projects are closely tied to funding milestones and reporting deadlines. Delays in surveys, design approvals or contractor mobilisation can threaten delivery windows, especially where access to suitably qualified coordinators or installers is restricted. In some cases, schemes may need to be rescoped or paused entirely if costs or risks escalate beyond what is viable.

Despite these pressures, PAS 2035 remains a powerful tool when used effectively. Beyond compliance, it enables estate-wide data gathering, informed prioritisation of investment and a shift away from the reactive, piecemeal upgrades that have historically undermined long term performance.

Having delivered around 800 PAS 2035 assessments, we have seen firsthand how proportionate application can unlock significant technical and strategic value.

The way forward is not to move away from PAS 2035, but to refine how it is deployed. By phasing interventions sensibly, tailoring assessments to risk, and aligning technical rigour with appropriate levels of investment, local authorities can strike a balance between quality assurance and delivery efficiency.