56 thaw cycles are recurrent (as in the case of the strong fluctuations in temperatures recorded in recent years due to climate changes). The mechanical stress to which the wooden material constituting the structure of the warehouses is subjected is caused by the greater volume occupied by the ice compared to the one occupied by liquid water. The liquid water that infiltrates into the pores and the voids of the wood, becoming ice below 0°C and increasing in volume, causes an increase in the size of the pores and the voids with consequent fractures and cracks. Due to climate change, we observe frequent freeze-thaw cycles also during winter, these are caused by the rise of average temperature. 5b) salt (sub)efflorescence: although there it is river water, its proximity to the sea makes it “mixed” and the capillary rising of salts through liquid water is a natural phenomenon for wet wood. The problem of the cycles increases when the water passes from the liquid form to the vapor form (evaporation) and the salts (mostly chlorides and nitrates) become insoluble in a smaller quantity of water (supersaturation of the solution) and crystallize in the pores and voids of the wood. Repeated cycles over time cause an increasingly marked crystallization. If the evaporation is fast (high temperature and presence of wind) the crystals are small in size and form below the surface → sub-efflorescence, if the evaporation is slow (low temperature, absence of sunlight and wind) the crystals are large in size → efflorescence. The greater intensity of climate fluctuations in temperature and humidity due to recent climate changes results in a greater speed of occurrence of the degradation phenomenon caused by the cycles of saline crystallization and dissolution. Requirements regarding preventive conservations methods, goals and possible solutions “Sustainability is the idea of using cunning, looking at what people did in the past, adding that to modern physics, and generally designing things that you're proud of because you didn't drag in a whole lot of electricity and energy." - Tim Padfield19” Considering the climatic risks, material vulnerabilities, heritage value and specific problems related to future uses, there are high requirements in terms of environmental control and preventive preservation. The main aim is to safeguard the warehouses as a cultural heritage while respecting its significance, integrity and authenticity. This includes its accessibility to present and future generations. In addition, in times of climate change and limited energy resources, the reduction of the carbon footprint should be a part of a holistic and sustainable approach. During the last decades, the idea of Passive Environmental Control [Pearson et al., 2000206] 19 https://www.getty.edu/conservation/publications_resources/newsletters/22_1/dialogue.html, accessed 29.05.2022. 20 Pearson, C. / King, S.: Passive Environmental Control for Small Cultural Institutions in Australia, in: Australian Academic & Research Libraries, 31/2/2000, 69-78, DOI: 10.1080/00048623.2000.10755117,
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