Guide to Conversion of Traditional Buildings

8.0 Sustainability and the historic environment

8.1 Climate change policy and targets

The Climate Change (Emissions Reduction Targets) (Scotland) Act 2019 committed Scotland to one of the most ambitious carbon reduction targets of reaching net-zero by 2045. The UK Green Buildings Council identified the built environment as a significant source of UK emissions, accounting for up to 42% (including surface transport). Reducing demand for new construction through the reuse of existing buildings and retrofitting them with energy efficiency measures will therefore be paramount in lowering this figure to tackle climate change.

The decarbonisation of heating systems will be central to reaching this target and will be mandated by the Scottish Government’s Heat in Buildings Bill in 2026. This will set out the minimum energy efficiency standards for all buildings to transition to clean heating by 2045. It will include the steps to be taken to reduce emissions from Scotland’s buildings which will also be achieved through a range of energy efficiency improvements to the fabric of existing buildings to reduce demand on heating (the main driver for retrofit).

Scotland’s planning policy framework set out in the National Planning Framework (NPF4 2023) includes detailed policy on historic places as outlined in chapter 6.1 above (Historic environment policy overview) of this guidance. Policy 1 of NPF4 relates to tackling the climate and nature crises and specifically states that this connects to all other policy areas.

National planning policy for the historic environment is set out in the ‘Historic Environment Policy for Scotland’ (HEPS 2019). This is a policy statement for guiding decision-making relevant to the whole of the historic environment, from local level to national. HEPS sets out six policies for the recognition, care and sustainable management of the historic environment which are set out above in chapter 6 (Heritage management structure). Among a range of challenges and opportunities facing the historic environment, HEPS acknowledges the need to address the impacts of climate change.

‘Our Past, Our Future’ (2023) is Scotland’s national strategy for the historic environment and sets out three priorities which align with the key Scottish Government ambitions. Priority 1 is about ‘Delivering the transition to net zero’ in response to climate change.

8.2 Operational and embodied carbon

The built environment currently contributes to 25% - 42% of the UK’s carbon emissions (direct emissions only to emissions including surface transportation) (Reference: UK Green Buildings Council). This figure is made up of two types of carbon: operational and embodied carbon. Operational carbon is related to the emissions associated with the energy that is used to operate a building (including heating, cooling and lighting). General practice has tended to focus on operational carbon when trying to reduce emissions in the built environment and be more sustainable.

Embodied carbon relates to the emissions associated with the materials and construction processes used throughout the whole life of a building, such as the materials extraction, the product manufacture, transportation to site, maintenance, repair, refurbishment and end-of-life processes. Embodied carbon is often overlooked, but both types of carbon contribute to emissions, so it is important that both are considered. Together, operational and embodied carbon can be used to calculate the Whole Life Carbon Emissions from a building.

One of the most effective ways to reduce carbon emissions in construction is to retain and reuse existing buildings. The embodied carbon associated with their initial construction has already been spent, therefore, by reusing and maintaining these buildings, and adapting them so that their operational carbon is lower (through low-emissions heating and fabric upgrades), this can significantly lower the overall carbon associated with their use.

This can save more carbon than demolition and replacement because, even though the higher energy efficiency standards of new builds may achieve lower operational carbon levels than a retrofitted building, the higher levels of embodied carbon from their construction outweigh the operational savings made over 60 years. In addition, the retrofitting of existing buildings saves carbon in the present, which will have a greater impact on the urgent need to address climate change sooner, rather than relying on predicted future carbon savings from new construction.

It should be noted, however, that energy efficiency improvement measures can also generate carbon. The level generated can vary depending on the materials selected, where they have come from, how they are made, how long they last, etc. As such, not all retrofits are inherently good from a carbon perspective. It is recommended that a sustainable approach to retrofit is followed to address this. This can result in an average of 85% less carbon in year 0 following retrofit, compared to demolishing and rebuilding, and around 30% less carbon than a lower-standard retrofit. What constitutes a sustainable approach is explained further below.

8.3 Adaptive re-use of traditional buildings

About 19% of Scotland’s domestic building stock is of traditional construction (typically referred to those built before or around 1919). This means they have a significant role to play alongside other existing buildings in reaching our carbon emission targets. Retaining, repairing and reusing our existing buildings saves embodied carbon and is the most sustainable thing we can do in the built environment.

However, uses and needs change, as well as our standards of living and comfort, which means that buildings may require upgrading or a new use, so they are fit for purpose and for the future. The sustainable practice of repurposing existing buildings that will secure their long-term future is often termed as ‘adaptive reuse’. For traditional buildings, it can provide a sustainable future with wider economic, social and cultural benefits, alongside the environmental ones.

A significant part of adaptation is making buildings more energy efficient, which is crucial to lowering their operational carbon. Clean, low-carbon heating and upgrades to fabric can greatly reduce the energy demand of a building, helping to meet lower carbon emissions targets. If a sustainable approach is taken to these upgrades, it can also deliver other benefits such as improvements to air quality and the comfort and wellbeing of occupants.

Traditional buildings were typically built with the local weather conditions in mind. This meant they were designed to deal with Scotland’s harsher climate and included weather detailing, primarily focused around the dispersal of rainwater and protection against wind and wind-driven rain. This has not only made them able to stand the test of time but also makes them well suited to cope with a changing climate with little adaptation. Whilst most traditional buildings have functioned perfectly well for many years with adequate maintenance, they may be becoming less able to do so as a result of the changing climate. They may, therefore, need to be adapted to increase their resilience against the effects of climate change, such as increased precipitation, floods, landslide, freeze-thaw cycles, ground movement, biological growth, storm damage and, generally, more extreme weather events.

These climate change-driven events can in turn create damper internal environments, raising humidity levels and encouraging the growth of mould, impacting on our health. As temperatures continue to rise in some areas, combined with stricter energy efficiency mandates which are focused on heat retention, this can create issues with overheating and increased relative humidity in buildings, often exacerbating existing issues associated with damp and lack of ventilation. Again, traditional buildings can offer a solution to this, as they were primarily designed with ventilation in mind. With clever adaptation of existing features or the re-introduction of lost ones, they can balance out any potential risks associated with increasing the thermal performance of building fabric and reduce unwanted air-infiltration, ensuring that a happy equilibrium is reached.

8.4 Sustainability in the built environment

Sustainability can have different interpretations, depending on the context. For the purposes of this guidance on the conversion of traditional buildings, sustainability means reusing a building and/or upgrading it, so that it is fit for purpose and for the future (to prolong its life), using eco-friendly materials and methods which are resource efficient and do not harm the environment. This can include upgrades to make it more energy efficient, adaptation of services, adaptation of architectural detailing to create/enhance resilience against the effects climate change, finding a new sustainable use and following a design ethos that is based on long-term resilience. Traditional buildings may then become part of a circular economy for a continuing reduction in carbon emissions, rather than be marginalised as ‘hard to treat’.

As the planet’s resources come under increasing pressure, the retention and reuse of our building stock is one of the most sustainable actions we can take. This is because it reduces the need for new buildings, therefore reducing construction-generated carbon and tackling resource scarcity.

However, to follow a sustainable approach, the upgrading of a building will require further actions and choices. This should include the retention and reuse of as much of the existing fabric as possible, allowing the building to evolve in a way that still retains its qualities. Many refurbishment projects involve a lot of work dismantling later interventions, such as lowered ceilings and blocked hearths. Retaining original linings and finishes is an effective way to reduce the need for new materials and the waste produced by a refurbishment project. Where new materials are needed, these should be locally sourced where possible, naturally derived or compostable, or be materials that can be reused. Technical compatibility with existing fabrics, such as using vapour permeable materials, following a whole-house approach in retrofit, maintaining ventilation for healthy indoor environments and continued maintenance, are equally important and part of a sustainable approach in refurbishment.

8.5 Traditional materials and a circular economy

Buildings of traditional construction are inherently sustainable. They were often built using less-intensive (low energy) methods and followed a ‘breathable construction’ approach, using vapour-permeable materials primarily found/extracted/grown locally. This reduced the need for transportation and complex supply chains and, as the processing of the materials was also often minimised, the embodied carbon of these materials was inherently low.

The methods, skills and people involved in their construction were also historically linked to locality, strengthening local economies and creating regional style variations, tightly linked to resource availability and the prevailing weather conditions of an area. There was historically no specified lifespan but were built to last, with most of them having lasted for over 100 years.

Maintenance of a building and its parts, rather than replacement, was the standard practice, with smaller scale but more frequent repairs being more common and often done by the building users themselves. At the end of their lives, the construction elements and naturally derived materials of these buildings could, in most cases, be reused or go back to the ground. That cycle continued almost indefinitely; a process that we nowadays refer to as a Circular Economy.

An additional benefit of some traditional materials is that they can capture carbon. Trees, for example, absorb and store carbon during their growth. When that tree is used as timber in building construction, that carbon remains locked in and can continue to do so for decades if responsibly managed. This is also the case with other grown materials used to create modern insulation products, such as hemp, wood fibre and sheep’s wool, as well as recycled-waste products, such as cellulose. Another such traditional material is building lime - whilst its production requires high heat which releases carbon emissions, lime can re-absorb it through the process of carbonation, and in some cases can continue to do so through the lifetime of a building.

Today, the increased use of synthetic – often high in VOCs – highly-processed, impermeable materials in building construction in favour of speed, cost and ease (through lack of skills required in their use/installation) has not only resulted in a linear economy - production, use and disposal - generating more waste and resource demand than ever before, but it has brought additional issues, such as poorer indoor air quality in buildings and risks related to condensation and damp, especially as buildings are being insulated in an effort to become more energy efficient. Materials in construction are also commonly imported, further adding to their higher embodied carbon compared to more local materials.

As resources are becoming increasingly finite/depleted, we ought to be looking into re-introducing a future based on a circular economy to eliminate or minimise waste. In conversions and refurbishments, this means repairing and reusing materials in situ as a first option, followed by repurposing them, if possible. Where new materials are required, they should be compatible with the building (i.e. vapour-permeable, if used in traditional buildings) and low in embodied carbon – usually these are mineral, plant or tree-based – seeking to capture carbon where possible, e.g. using timber for framing insulation and a plant-based insulation batt, and lime for pointing. The end of life of construction materials should also be considered, including the costs for disposal of materials. This can assist in working out the overall carbon expended in a building refurbishment and mitigate higher operational emissions, where fabric cannot be improved beyond a certain point.

Where traditional buildings are being converted, they are required to comply with the Building Regulations, but this does not necessarily dictate the use of modern materials. With the right advice and appropriate detailing, traditional buildings can be improved to meet modern standards, while still functioning in the way they were designed, allowing the dispersal and movement of water vapour through their fabric.

8.6 Further reading

• The Climate Change (Emissions Reduction Targets) (Scotland) Act 2019
• Scottish Government’s Heat in Buildings Bill (to be published 2026)
• Historic Environment Scotland (2019) The Historic Environment Policy for Scotland
• Historic Environment Scotland (2023) Our Past, Our Future