Historic buildings account for more than one-quarter of Europe’s existing building stock and are going to be crucial in the achievement of future energy targets. Although a drastic reduction in carbon emissions would slow climate change, an alteration in the climate is already certain. Therefore, the impact of climate change on retrofitted historic buildings should be considered in terms of occupants’ comfort, heritage conservation, and energy performance. Inappropriate interventions might weaken the potential of traditional climate adaptive solutions, such as thermal mass and night cooling, leading to higher risks of overheating in a warming climate. Similarly, retrofit solutions will change the moisture dynamics of historic envelopes, which might lead to moisture damages when combined with more extreme precipitation events. This paper reviews recent literature that provides evidence of climate change’s impact on retrofitted buildings, reveals potential future risks, and thereby sheds light on new factors influencing the decision-making process in the retrofit of historic buildings.

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.

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.

Historic building restoration and renovation requires sensitivity to the cultural heritage, historic value, and sustainability (i.e., building physics, energy efficiency, and comfort) goals of the project. Energy-efficient ventilation such as demand-controlled ventilation and heat recovery ventilation can contribute to the aforementioned goals, if ventilation concepts and airflow distribution are planned and realized in a minimally invasive way. Compared to new buildings, the building physics of historic buildings are more complicated in terms of hygrothermal performance. In particular, if internal insulation is applied, dehumidification is needed for robust and risk-free future use, while maintaining the building’s cultural value. As each ventilation system has to be chosen and adapted individually to the specific building, the selection of the appropriate system type is not an easy task. For this reason, there is a need for a scientifically valid, systematic approach to pair appropriate ventilation system and airflow distribution solutions with historical buildings. This paper provides an overview of the interrelationships between heritage conservation and the need for ventilation in energy-efficient buildings, regarding building physics and indoor environmental quality. Furthermore, a systematic approach based on assessment criteria in terms of heritage significance of the building, building physics (hygrothermal performance), and building services (energy efficiency, indoor air quality, and comfort rating) according to the standard EN 16883:2017 are applied.

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.