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Internal insulation plasters enable historic building renovation without altering the external appearance of the wall. However, the use of internal insulation must be verified case-by-case through dynamic hygrothermal simulation, and the influence of input parameters on the results is not always clear. This paper aims to (i) characterize a new lime-based insulating plaster with expanded recycled glass and aerogel through laboratory measurements, (ii) assess the damage criteria of the plaster under different boundary conditions through dynamic simulations, and (iii) identify the most impactful design conditions on the relative humidity behind insulation. This innovative plaster combines highly insulating properties (thermal conductivity of 0.0463 W/mK) with good capillary activity while also integrating recycled components without compromising performance. The relative humidity behind insulation remains below 95% in most simulated scenarios, with cases above this threshold found only in cold climates, particularly under high internal moisture loads. The parametric study shows that (i) in the analyzed stones, the thermal conductivity variation of the existing wall has a greater effect on the relative humidity behind insulation than the variation of the vapor resistance factor, (ii) the effect of insulation thickness on the relative humidity behind insulation depends on the difference in thermal resistance of the insulation and existing masonry layers, and (iii) internal moisture load and external climate directly impact the relative humidity behind insulation.

Energy retrofits can enhance the liveability and efficiency of historic buildings while preserving their historic and aesthetic values. However, measures like improved insulation and airtightness may increase their vulnerability to overheating and climate change may further worsen their performance in the future. This paper investigates indoor overheating risks brought by climate change in retrofitted historic buildings and proposes effective adaptation strategies. Firstly, local weather conditions are analysed to identify homogenous climatic zones. For each climatic zone, “a business-as-usual” emissions scenario is adopted, and most representative regional climate models are selected to obtain hourly output of future climate projection. A comparative study is adopted where typical alpine residential buildings, “Portici house”, are simulated with regard to future energy use and indoor thermal state using the dynamic model in EnergyPlus. Energy use and indoor thermal conditions are compared before and after energy retrofit, as well as under present and future climate conditions. The results demonstrate that retrofit interventions could significantly improve energy efficiency of historic buildings in both present and future scenarios. A change in climate together with retrofit interventions will, however, result in higher risk of indoor overheating in South Tyrol. Potential negative side effects of energy retrofit could be controlled by adopting adequate shading and ventilation approaches that minimise, or eliminate, the risk of overheating during high temperature periods while optimising historic buildings’ energy performance.

This handbook holistically summarises the principles for the energy retrofitting of historic buildings, from the first diagnosis to the adequately designed intervention: preservation of the historic structure, user comfort, and energy efficiency. The content was developed by an interdisciplinary team of researchers. The wide range of different expertise, design examples, calculations, and measuring results from eight case studies makes this manual an indispensable tool for all architects, engineers, and energy consultants.

The hygrothermal behaviour of an internally insulated historic wall is still hard to predict, mainly because the physical characteristics of the materials composing the historic wall are unknown. In this study, the hygrothermal assessment of an internally thermal insulated masonry wall of an historic palace located in Ferrara, in Italy, is shown. In situ non-destructive monitoring method is combined with a hygrothermal simulation tool, aiming to better analyse and discuss future refurbishment scenarios. In this context, the original U-value of the wall (not refurbished) is decreased from 1.44 W/m2K to 0.26 W/m2K (10 cm stone wool). Under the site specific conditions of this wall, not reached by the sun or rain, it was verified that even in the absence of vapour barrier, no frost damage is likely to occur and the condensation risk is very limited. Authors proposed further discussion based on simulation. The results showed that the introduction of a second gypsum board to the studied technology compensated such absence, while the reduction of the insulation material thickness provides a reduction of RH peaks in the interstitial area by 1%; this second solution proved to be more efficient, providing a 3% RH reduction and the avoidance of further thermal losses.

The challenge of transforming historic buildings and city centers into energy-self-sufficient environments requires innovative solutions. The research project “BiPV meets History” addressed this challenge by providing comprehensive guidelines for assessing the integration of photovoltaic (PV) systems in protected historic architectural contexts. To validate these guidelines, this study conducts a thorough examination of best practices through the mentioned guidelines, developing an application tool. Recognizing the power of well-communicated best practices in overcoming obstacles to integrated photovoltaic adoption, this tool is used to assess PV integration quality with respect to the best practice contained in the HiBERatlas database. The analysis of 17 successful refurbishment cases highlighted the robustness and reliability of the proposed methodology, considering aesthetic, technical, and energy aspects. This study emphasizes the potential of the guidelines for achieving a harmonious integration of renewable energy solutions with historic architectural heritage and landscape and improving usability through the developed tool.

The abandonment and deterioration of historic rural buildings in Europe raise significant issues, including hydrogeological risks, the loss of productive land, and cultural heritage decline. Despite being underestimated, these structures hold significant potential for cultural and productive activities. Renovating these structures is crucial for local communities committed to preserving their heritage, and it is a more sustainable approach than constructing new buildings. This study explores activities undertaken in the Interreg IT/AT project “SHELTER” in Valbrenta (IT): through a participatory approach involving communities, stakeholders, designers, and researchers, an energy concept is developed for refurbishing an abandoned tobacco farm, chosen by the community, to be an alpine hut. Due to the inability to connect to the city electricity grid, the new energy concept focuses on minimizing consumption through envelope refurbishment, efficient heating, and domestic hot water systems. Additionally, the integration of renewable energy sources, particularly Building Integrated Photovoltaics (BIPV), is emphasized to preserve the building’s original appearance. This study demonstrates the feasibility of meeting seasonal energy needs entirely through renewables and explores the potential integration of biomass for meeting annual energy requirements.

This study investigates the social acceptance of integrated photovoltaic (IPV) systems in heritage and landscape contexts, focusing on Italian stakeholders in the construction sector. As part of the “BIPV meets History” research project, this study aims to identify barriers, potentials, drivers, and challenges for widespread PV technology adoption, considering heritage conservation, land preservation, energy production, and climate mitigation. A survey exploring opinions on PV technology integration was conducted. The survey was improved and extended to a total of 271 respondents, using the online method of Computer-Aided Web Interviewing (CAWI), to understand how perceptions of integrated photovoltaics have changed after COVID-19 and the European energy crisis, emphasizing aesthetic, environmental, economic, and personal aspects. The results indicate a general awareness of the technologies, with increasing acceptance in protected contexts, for historic buildings (from 51 to 68%) and especially landscapes (from 44 to 71%), driven by energy and environmental benefits. Cultural concerns, particularly the risk of impacting historical and natural identities, emerge as major barriers. Additionally, it is evident that awareness of PV panel recycling methods is still limited.

This study presents an in-depth analysis of 69 case studies focusing on the energy retrofit of historic buildings, uncovering challenges, best practices, and lessons learned to balance energy efficiency improvements with heritage preservation. The findings highlight several challenges encountered during renovations, such as complex heritage evaluations, restrictions on alterations, coordination issues with authorities, technical limitations, higher investment costs, and knowledge gaps. On the other hand, identifying factors promoting renovation, including demonstrating energy savings while respecting heritage, early collaboration between planners and authorities, and quantifying investments, could incentivize owners and authorities. The limitations of a still-limited sample size, occasional incomplete data, and potential sample bias call for cautious interpretation of the presented analysis. Despite these, the study provides valuable insights into successful projects, emphasizing the need for scalability, knowledge transfer from innovative policies, and targeted policy-making for successful replication. The study concludes with a call for further development of the HiBERatlas (Historic Building Energy Retrofit atlas), an extensive resource for historic building renovation, expanding its database, collaborating with agencies, and tailoring guidance for stakeholders to foster energy retrofits in heritage buildings.

Thermal modeling of building components plays a crucial role in designing energy efficiency measures, assessing living comfort, and preventing building damages. The accuracy of the modeling process strongly depends on the reliability of the physical models and the correct selection of input parameters, especially for historic buildings where uncertainties on wall composition and material properties are higher. This work evaluates the reliability of building thermal modeling and identifies the input parameters that most affect the simulation results. A monitoring system is applied to a historic building wall to measure the temperature profile. The long-term dataset is compared with the result of a simulation model. A sensitivity analysis is applied for the determination of the influential input parameters. A two-step optimization is performed to calibrate the numerical model: the first optimization step is based on an optimized selection of the database materials, while the second optimization step uses a particle swarm algorithm. The results indicate that the output of the simulation model is largely influenced by the coefficients describing the coupling with the boundary conditions and by the thermal conductivities of the materials. Very good results are obtained already after the first optimization step (RMSE=0.75 °C) while the second optimization step improves further the agreement (RMSE=0.48 °C). The parameter values reported in the datasheets do not match those found through optimization. Even with extensive optimization using an algorithm, starting with monitoring data is insufficient to identify material parameter values.

Humidity, salt content, and migration in building materials lead to weathering and are a common challenge. To understand damage phenomena and select the right conservation treatments, knowledge on both the amount and distribution of moisture and salt load in the masonry is crucial. It was shown that commercial portable devices addressing moisture are often limited by the mutual interference of these values. This can be improved by exploiting broadband radar reflectometry for the quantification of humidity in historic masonry. Due to the above-mentioned limitations, today’s gold standard for evaluating the moisture content in historic buildings is still conducted by taking drilling samples with a subsequent evaluation in a specially designed laboratory, the so-called Darr method. In this paper, a new broadband frequency approach in the range between 0.4 and 6 GHz with improved artificial-intelligence data analysis makes sure to optimize the reflected signal, simplify the evaluation of the generated data, and minimise the effects of variables such as salt contamination that influence the permittivity. In this way, the amount of water could be determined independently from the salt content in the material and an estimate of the salt load. With new machine learning algorithms, the analysis of the permittivity is improved and can be made accessible for everyday use on building sites with minimal intervention by the user. These algorithms were trained with generated data from different drying studies on single building bricks from the masonries. The findings from the laboratory studies were then validated and evaluated on real historic buildings at real construction sites. Thus, the paper shows a spatially resolved and salt-independent measurement system for determining building moisture.