## 1 Introduction  
Preventive conservation of heritage collections plays an important role in minimizing climate-induced decay and avoiding detrimental effects when they are maintained in an indoor environment as stable as possible [1]. As many of these collections are composed of organic materials such as paper, which shrink and expand with dropping and rising moisture content, especially fluctuations in relative humidity (RH), they should be avoided to prevent mechanical damage at a fast strain rate in the storage space of libraries, galleries, and museums [2]. Climate change exacerbates this risk, accelerating degradation, increasing conservation costs, and making climatization necessary [3]. While maintaining a stable environment is essential, it requires precision air conditioning with tight control, resulting in substantial energy consumption and carbon emissions [4; 5]. Effective conservation and protection of heritage collections require well-informed management tools grounded in an understanding of how environmental parameters evolve over time and vary across the environment [6]. In addition, a great number of collections are usually stored in some European historic buildings with poor energy performance, posing a challenge for retrofitting the buildings where exterior facades are decorated with carvings and sculptures, while interior walls are decorated with frescoes [7]. Consequently, improving operational energy efficiency is a challenging task for achieving sustainable preventive conservation. Many approaches have been developed for controlling the micro-environment within enclosures rather than the whole macro-environment in the room. Adding some buffering materials inside the enclosures to achieve passive control is a prevalent approach [8]. The enclosure separates the micro-environment inside from the macro-environment, and the room where the enclosure is present and the confined space with buffering materials provide a degree of hygothermal buffering effect. In the National Library of Scotland (NLS), the paper-based enclosures are used for storing books in storage rooms, like many other cultural institutions. These enclosures are created from functional cardboard with specific elements and a porous structure. The cardboard consists of three layers: an external waterproof layer, a middle multi-thin layer, and an internal lining layer. The external layer contains polypropylene to provide waterproof and thermal-insulation functions [9; 10]. The middle and inner layers contain pulp cotton and calcium carbonate to regulate the micro-environmental temperature and humidity [11; 12]. To consider fabric permeability, a thin multi-layer structure is designed in the middle layer to increase the tortuosity of porous channels. This design can increase moisture retention through small air gaps between these layers, thus improving the buffering effect [13]. The enclosures can stabilize the micro-environment, especially mitigating fluctuations in RH due to their buffering effect. This buffering effect has been rigorously evaluated in a laboratory test [14]. It quantified the enclosure's capacity to minimize the micro-environmental fluctuations over some given periods under two distinct macro-environmental conditions (10 %RH fluctuation within 50-60 %RH at a fixed 20 \({}^{\circ}\)C for the humidity buffering test; 5 \({}^{\circ}\)C fluctuation within 17-22 \({}^{\circ}\)C at a fixed 50 %RH for the temperature buffering test). The results demonstrated that the micro-environmental fluctuations are 2-8 %RH and 1-2 \({}^{\circ}\)C smaller than the macro-environmental ones. These findings suggested that the enclosures can provide a degree of buffering capacity to mitigate micro-environmental fluctuation by reducing their response to that of the macro-environment. Such buffering capacity enables a relaxing control for macro-environment when the micro-environment complies with the standards of preventive conservation.