Retrofitting Traditional Buildings: Insights from Professor John Edwards at RIBA Berkshire

We recently had the opportunity to attend a thought-provoking lecture hosted by RIBA Berkshire, titled “Retrofitting Traditional Buildings”, delivered by Professor John Edwards of Edwards Hart Consultants. The session was an examination of the critical nuances of upgrading historic and traditional buildings to meet modern performance standards—without compromising their heritage value. 

Here are some key takeaways that stood out: 

The key distinction between traditional and modern buildings typically hinges on the 1919 Addison Housing Act, which marks a general cut-off point. Around a third of UK buildings predate this Act and are thus considered traditional in construction. 

Whether it’s a Victorian terrace or a Grade I listed castle, these buildings often share similar construction characteristics. The difference? Usually just the level of statutory protection they’re afforded. 

Professor Edwards stressed the importance of understanding the standards—many of which are shaped by vested interests—and choosing the right ones can be tricky: 

• PAS 2035 (commonly applied to domestic retrofit projects) has significant shortcomings, particularly its minimal training requirements (a 2-day course is all that’s needed to become an assessor). 

• PAS 2038, on the other hand, focuses on non-domestic buildings and is a more robust and competency-led standard. Encouragingly, it also embeds BS 7913, a well-regarded document in the conservation world. 

• The soon-to-be-released BS 40104 is one to watch—it promises stronger guidance. 

• The IHBC Guidance, which is free, provides a solid process-based approach. 

The retrofit of traditional buildings should follow a wholistic, step-by-step approach: 

1. Understand the Significance 
   Engage with Conservation Officers, Historic England, and understand why the building matters. 

1. Retrofit Assessment 
   Look at the technical aspects, current use, and environmental context. This should be done by qualified assessors. 

1. Energy Efficiency Assessment & Modelling 
   Assess how the building performs and simulate retrofit options. 

1. Decide on Retrofit Options 
   Use the PAS2035:2019 Measure Interaction Matrix to avoid conflicting interventions. The STBA retrofit wheel is a great visual tool for this. 

1. Heritage Impact Assessments 
   Justify the need for retrofit, evidence the existing performance (e.g., U-values based on actual materials), and use hydrothermal modelling to avoid moisture risks. The process should cover the proposal, location, rationale, supporting research, potential impact, mitigation strategies, and alternative options. 

1. Finalise Proposals 
   Design and specify measures, ensuring compatibility and reversibility. 

1. Implementation 
   Execute the work as designed. Many retrofits fail due to poor delivery that doesn’t match the modelling, leading to moisture issues and a performance gap. 

1. Audit and Evaluate 
   post-implementation review is crucial to ensure long-term success. 

Moisture was a recurring theme throughout the lecture. It’s the biggest threat to both the performance and preservation of historic buildings. Any retrofit must design out moisture, particularly when introducing insulation. Materials must be hygroscopic and breathable—wood fibre insulation is an excellent example, offering both thermal mass for summer cooling and warmth in winter. 

While PAS2035 mentions “fabric first” as a guiding principle, this can be risky and inappropriate for traditional buildings. Instead, Professor Edwards advocates for a risk-based approach that considers the unique vulnerabilities and significance of older structures. 

For more in-depth training and tools on sustainable retrofitting and building performance, Professor Edwards recommends www.environmentstudycentre.org. 

Retrofitting traditional buildings is as much about preservation as it is about performance. It demands a carefully balanced approach, underpinned by sound knowledge, appropriate standards, and qualified professionals. As Professor Edwards made clear, what we do—and how we do it—can either safeguard or irreparably harm our built heritage. 

At iB Architects, these insights resonate strongly with the way we approach our own retrofit and refurbishment projects. Many of our commissions involve breathing new life into older buildings—carefully enhancing their performance while respecting their character and significance. 

Professor Edwards’ emphasis on a step-by-step, risk-based methodology mirrors our own design process. We know that a “fabric first” approach isn’t always appropriate for traditional structures; instead, we prioritise thorough assessments, moisture‑aware detailing, and the use of compatible materials to ensure interventions are both effective and sympathetic. 

For clients considering upgrades to a historic or traditionally built property—whether commercial or residential—we bring together conservation expertise with modern technical know‑how. From early feasibility studies through to detailed design and delivery on site, we help unlock the potential of existing buildings without compromising their heritage value. 

If you are planning a retrofit project and want to ensure it meets today’s sustainability goals while safeguarding the qualities that make your building unique, we’d be delighted to support you.

Get in touch with us to discuss how we can help turn those principles into a successful, future‑ready project.