Breathing new life into the past: Sustainable retrofits for Edinburgh's heritage buildings

Scotland’s historic environment has been shaped by people since the first settlements identified from 12,000 BC, leaving an indelible mark on its towns, cities and countryside. This rich heritage provides a sense of place and cultural identity rooted in communities and is celebrated worldwide.

Edinburgh, a city renowned for its rich architectural heritage, faces a unique challenge of balancing the preservation of historic structures with the urgent need for sustainability. Whilst alluring and culturally significant, heritage buildings often come with outdated energy systems, poor insulation and inefficiencies that make them damaging to the environment.

With around 40% of Scotland’s total carbon emissions stemming from domestic energy consumption and nearly 20% of all buildings being of traditional construction, improving the energy efficiency of these buildings is crucial to achieving national carbon reduction commitments under the Climate Change (Emissions Reduction Targets) (Scotland) Act 2019 whilst maintaining the cultural heritage of our nation. This act also aims for net zero emissions by 2045, five years ahead of the UK’s zero emission target in 2050.

Heritage buildings pose unique challenges for retrofitting. Strict conservation regulations, fragile building materials and architectural significance often limit the scope of modern upgrades. The use of inappropriate materials or intrusive techniques can risk irreversible damage to the historical fabric of these structures. Respecting the aesthetic and cultural value of these structures while improving energy efficiency and reducing carbon footprint is essential. Despite these challenges, historic and traditional buildings are central to Scotland’s landscape and identity. They are adaptable and robust, with features such as permeable materials and passive ventilation mechanisms designed to manage moisture and climate effectively, which require tailored retrofit approaches to avoid disrupting the original functionality. Additionally, the vernacular materials and irregular geometry commonly associated with historic buildings further complicate retrofitting efforts, necessitating careful, site-specific solutions.

Historic Environment Scotland underscores the importance of integrating historic and traditional buildings into national retrofit programmes to meet ambitious carbon reduction targets. This can be achieved by combining modern retrofit techniques with conservation principles. Successful sustainable retrofitting relies on principles such as:

• Minimal intervention: Ensuring upgrades are non-invasive and reversible to maintain the building's historical integrity.
• Energy efficiency: Improving insulation, windows and heating systems to reduce energy consumption without altering the building’s appearance.
• Material sensitivity: Using sustainable and compatible materials that align with the original construction methods.
• Holistic design: Considering the building's original design, purpose and current environmental challenges.

The importance of balancing energy performance improvements with the need to preserve historic fabric and character lies in achieving sustainability goals while maintaining the integrity and uniqueness of these buildings. Retrofits are now considered the tool for the job.

Examples of proven retrofit techniques include:

• Secondary glazing: Installing internal secondary glazing systems to improve thermal efficiency while preserving original windows.
• Double glazing: Installing heritage compliant vacuum glazing or slimline glazing systems will improve the thermal efficiency while preserving the aesthetic and architectural integrity of original windows.
• External doors improvements: The panels can be upgraded by applying a thin layer of high-performance insulation, such as an aerogel-based material, to the rear of the existing door panel(s).
• Breathable insulation: Applying natural, breathable insulation materials such as sheep’s wool to maintain moisture balance and prevent deterioration.
• Smart technology: Implementing energy monitoring systems to optimise energy use and identify inefficiencies.

Scotland’s historic and traditional buildings serve as a testament to the vision and skills of past generations. These structures—ranging from croft houses and tenements to mills and places of worship—represent varied and exceptional heritage. Having stood for centuries, these buildings offer a unique perspective on long-term embodied carbon implications that extend far beyond the conventional 60-year lifespan assumed in modern assessments. Their adaptability and use of sustainable materials make them assets in achieving national carbon reduction goals. Owners and occupiers of listed buildings play a crucial role in managing this heritage, ensuring it can be passed on to future generations while contributing to Scotland’s ambitions for a net zero carbon future.

Lessons from international studies emphasise the importance of leveraging technological synergies into retrofits. For example, applying combined technologies to historic buildings, as seen in case studies in the Mediterranean Sea (Greece, Italy, Cyprus), reduced energy demand by up to 56% and shortened payback periods by more than 50%. The combined technologies in these case studies included window substitution and shading devices, thermal coat application and roof insulation as well as installation of PV panels, upgraded HVAC, lighting equipment and BEMS (Building Energy Management Systems). While these case studies focused on different climate zones, such practices could still inspire future retrofitting efforts in Edinburgh, positioning it as a leader in combining heritage preservation with modern sustainability goals. By leveraging tailored solutions—such as internal insulation systems that preserve external façades or smart ventilation systems that complement natural airflow—retrofits can enhance both the energy efficiency and longevity of Edinburgh’s heritage buildings. These approaches also ensure compliance with evolving regulatory frameworks that increasingly prioritise energy efficiency even in protected buildings.

Adopting a circular economy approach is integral to the sustainable retrofitting of heritage buildings. By prioritising the reuse of materials, minimising waste and integrating renewable resources (where suitable), retrofitting can extend the life cycle of building components while reducing their environmental footprint. Historic buildings, with their inherently durable construction and use of traditional materials, are ideal for implementing sustainable practices that extend the lifecycle of these structures and reduce environmental impact. Sustainable retrofits require collaboration between conservation experts, engineers, architects and policymakers. Organisations like the Edinburgh World Heritage Trust emphasise the importance of partnerships in achieving balance between preservation and sustainability goals. By combining engineering innovation with a respect for the past, we can breathe new life into these cherished landmarks for generations to come.