Impact assessment of climate change on tangible cultural heritage

Abstract

The present Ph.D. thesis quantitively examines the impact of climate change on specific cultural heritage (CH) assets, focusing on two historic timber buildings, two pieces of furniture, and brick masonry walls located in Tønsberg, southern Norway. The research employs experimental methods to analyse the deterioration of these assets and implements numerical simulations to assess future deterioration risks and to propose adaptation measures. The thesis contributes to the existing literature on quantifying the deterioration of tangible CH in the context of climate change through several key advancements. First, it investigates case studies which have not been studied before. Second, it intends to simulate the deterioration of the CH assets in high accuracy, by taking into account the temperature and humidity conditions on the material level, the material properties and other unique characteristics of the items of interest. This is achieved by combining appropriate hygrothermal and deterioration models. Additionally, within the context of improving the accuracy of the simulations of the historic timber building, a methodology was introduced which leverages material properties from an existing database, measurements and simulations of the hygrothermal performance of specific building elements, and a statistical index to ultimately select the material properties for the timber buildings. Third, the thesis utilizes data from a climate reanalysis to evaluate the accuracy of climate model results. Lastly, it compares the results of climate-based and material response-based risk assessment approaches in context of climate change. The thesis provides a comprehensive overview of the underlying concepts and theories, including details on the heat, air, and moisture (HAM) transfer software that has been used, global and regional climate models, representative concentration pathways, the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis. The experimental part of the thesis documents the deterioration patterns and mechanisms of the CH assets of interest. Part of it is the analysis of samples of fungi collected from the two timber buildings. Moreover, the monitored HAM performance of the two case studies is used for a better-informed selection of the material properties used within the numerical models. Whole-building HAM models are utilized to calculate temperature and relative humidity of materials or indoor air under climate change scenarios. The outputs of these simulations are then used in damage functions and deterioration models. For the timber buildings, the risk of mould growth on building components is assessed, while the investigation of the furniture covers mould growth, insect attack, chemical and mechanical deterioration risks. The brick masonry walls are evaluated for frost damage risk. Further, simulations employing climate v reanalysis data are conducted to assess the accuracy of climate model results. The thesis also presents a comparison between material response-based risk assessment (for timber and brick masonry components) and climate-based assessment. Survey results indicate a significant risk of fungal deterioration for the timber buildings, with the biological infestation predominantly observed on horizontal and north-oriented timber surfaces.Moreover, the two pieces of furniture exhibit notable mechanical deterioration, fading, and embrittlement of the paint. Finally, the brick masonry walls have shown granular disintegration and cracking, with the damaged bricks primarily found on facades facing southeast, south, and southwest. Simulation results reveal an increasing mould risk for untreated timber surfaces due to climate change, particularly on horizontal and north-oriented surfaces. On the contrary, treated surfaces show no mould risk. Recommendations include replacing rot-infested building elements, cleaning and treating degraded exterior areas, interior cleaning, removal of organic materials, and improving natural ventilation by opening doors during working hours. Increased mechanical and chemical deterioration risks are calculated for the furniture under present and future conditions, with the possibility of favourable conditions for temperature-dependent insect growth in one of the furniture-housing rooms. Relocation to a conditioned room is highly recommended. For the brick masonry walls, there is a decreasing trend in frost damage risk due to climate change. Unconditioned rooms with southeast-facing walls are experiencing the highest risk, while conditioned rooms with northwest and west orientations are facing the lowest risk. The comparison between climate-based and material response-based approaches indicates that the latter provides a better-informed deterioration risk assessment, accounting for microclimate and material properties of building components. The thesis concludes that future research shall improve the limitations of the current work and further include an economical perspective into the deterioration risk assessment.