4.2.3. Value

Some interviewees perceived preserving the values of cultural heritage as a barrier to climate change mitigation, because it limits the refurbishment options to make historical buildings more energy e fficient. This is because the measures adopted when retrofitting heritage assets can a ffect the heritage value, notably when historical elements are removed and replaced. Preserving the values of cultural heritage on the one hand and the implementation of measures to reduce the carbon footprint of heritage assets on the other hand should always be carefully balanced in any refurbishment project and, in this respect, buildings of diverse ages and listing category should be considered di fferently. The interviewees highlighted that preserving heritage value, authenticity and integrity should be prioritized when considering adaptation measures and strategies, as once the historical materials are removed and destroyed they will be lost forever. For this reason, the interviewees suggested alternatives to refurbishing buildings of high heritage value, such as integrating them as part of district energy networks, as described in Section 4.1.6, with the curbed CO2 emissions from retrofitted buildings used to o ffset the higher energy used in historical buildings.

One interviewee further added that it would be beneficial to have examples of public building refurbishment that preserve the value, integrity and authenticity of the heritage as models for others to follow: *"Long-term adaptation planning has to be done first in public buildings to be an example for the private."* (Table 3). Another interviewee representing a governmen<sup>t</sup> organisation recommended selecting adaptation measures that would not conflict with the heritage value: *"Where we had (...) a potential for losing the values, we just do not go there. We would rather do something else*.*"* An example of the latter is restoring historical wooden windows by inserting a secondary glazing with magnets, which can be removed during the warmer season, rather than replacing the windows with new ones. When refurbishing historical buildings, evidence is needed to justify retrofitting changes that influence the value, integrity and authenticity of the building. If restoration impacts on the value of those building, their historical meaning could be lost [51]. Historic Environment Scotland (HES), a governmental institution in charge of preserving cultural heritage in Scotland advises on the unrealistic expectation that historical buildings can reach energy e fficiency levels similar to new constructions but also advises for adaptive solutions that preserve the value, identity and significance of those assets to the community [61]. Furthermore, it should be emphasized that if the refurbishment of historical buildings can be seen as a threat to the heritage values, retrofitting can also constitute an opportunity to protect buildings, for example to heritage buildings in disuse or to those with minimal maintenance carried out [43].

### 4.2.4. Material Procurement and Sustainability Certification

The interviewees identified material procurement used during refurbishment of cultural heritage buildings as a barrier to climate change mitigation, as well as weaknesses in building sustainability certifications. With globalization, building materials are increasingly imported from other countries and, during the production process, they often travel from various locations around the world before reaching the construction site. The more a material travels, the more GHG emissions are derived from its transportation. However, the interviewees highlighted that in some cases, energy calculations and sustainability certifications do not consider the energy associated with transportation out of the country where the building is located. This can put foreign building materials at an advantage with regard to costs and certification, and this can influence the lack of locally sourced material during the refurbishment of historical buildings. The interviewees emphasized that the use of foreign materials not only increases GHG emissions, but may also not have the same characteristics as the original materials. There is also a lack of consideration of the energy embodied in the historical materials in energy evaluations. In fact, it was stated that historical buildings are not considered in performance

qualification and building standards and that energy evaluation software are not accurate in calculating the energy used by historical buildings.

The interviewees also reported a lack of consideration of the physical behaviour of heritage buildings and of the vapour permeability of historical material and an inaccuracy of Energy Performance Certificates (EPC) that make assumptions about energy use but do not reflect the actual performance of historical buildings. Incomplete Environmental Product Declarations (EPD) can also contribute to this issue [62], and, consistent with this, Cassar [51] stressed that some sustainability certification tools do not use a holistic approach; they are based on relative energy targets and they exclude social and economic sustainability aspects. In addition, Webb [43] emphasised the lack of consideration of embodied energy during the retrofitting of historical buildings, stressing the need for improved simulation tools and software to reduce the gap between simulations data and real building performance.

### 4.2.5. User Behaviour

User behaviour is considered a barrier to climate change mitigation because certain attitudes can minimise or even nullify the refurbishment efforts aimed at decreasing the use of energy by the building. The interviewees identified resistance to change and to the adoption of sustainable behaviours, for example, leaving the lights on during the day when there is high luminosity from the window, wearing light clothes in the winter and turning the thermostat up to a level beyond comfort level, to name a few. An interviewee also mentioned the rebound effect, which is a decrease in the expected energy savings from a specific building alteration because of behavioural change leading to an increase in energy consumption. For instance, in buildings were measures were introduced to use less electricity by installing heat pumps, people further increased their energy consumption by setting room temperature to a higher level on their thermostat. Sabbioni et al. [8] even proposed a change on a regulatory level to induce a modification in user behaviour.

### 4.2.6. Lack of Knowledge

The interviewees identified a lack in knowledge as a barrier to mitigate climate change in the built heritage sector. More research testing the use of modern materials during the refurbishment of historical buildings and on the traditional behaviours and characteristics of historical building is needed. Some interviewees also identified the need for more knowledge transfer to users on the topic of climate change mitigation in the field of cultural heritage in a way to make them more aware and capable of making choices compatible with the traditional behaviours and values of historical buildings.

### 4.2.7. Loss of Traditional Skills

Another significant barrier identified by the interviewees is the progressive loss of traditional skills and techniques. Given the common incompatibility of modern solutions with historical buildings and materials, this loss can threaten heritage preservation. The need to pass on knowledge and skills to the next generation of heritage professionals, and the importance of teaching traditional skills and techniques, and to understand how they relate to modern construction materials is emphasised in the literature, as well as methods on how to develop suitable conservation techniques appropriate with the nature of older buildings [51,63].

### 4.2.8. Incompatible Solutions

When refurbishing historical buildings, the adoption of solutions that are not compatible with the behaviour of historical materials can accelerate their degradation. For instance, the interstitial condensation between layers made of different materials. The traditional behaviour of the historical buildings, their thermal-balance, the natural ventilation of their indoor environments, and the ability of some historical materials to allow vapour movement are characteristics that must be taken in consideration during a refurbishment project. More research is needed on the evaluation of market-based solutions, which are usually designed for new structures but that are also applied to

historical buildings. Historical buildings have more sophisticated bioclimatic properties than modern constructions, and new materials that are incompatible with the physical behaviour of the historical ones can lead to an increase in decay. Retrofitting measures can alter the moisture balance of historical buildings, a ffecting, for example, their breathability, leading to an increase in the deterioration of historic materials [43,48]. Those buildings are designed to have controlled thermal comfort based on the natural unconditioned climate, environmental and site conditions rather than using machine-driven systems. The development of adaptation strategies should therefore consider the balance between decay reduction and energy consumption improvement of historical buildings [64,65].
