# Characterization of Responsive Plasters for Passive Moisture and Temperature Control
## 1 Introduction  
The energy consumption of the building sector still represents a substantial issue considering the population boom and increased thermal comfort requirements [1]. The utilization of heat, ventilation, and air-conditioning (HVAC) devices goes with noticeable energy consumption, and the building sector contributes almost 40% of the total energy consumption. In other words, substantial improvements need to be achieve in order to reach the nearly zero-energy building targets and the overall mitigation of the negative environmental impact of the building sector [2]. The energy efficiency of buildings depends substantially on the hygrothermal parameters of materials applied in building envelopes [3]. In this sense, a detailed characterization of heat and moisture transport, including the storage parameters of building materials, plays a crucial role within the optimization and design of energy-efficient building envelopes [4; 5; 6]. The potential improvements in the ambient thermal comfort were studied in detail, predominantly via the optimization of the building envelope layers, including the application of advanced insulation materials such as vacuum-insulationpanels and aerogels, or based on passive energy storage systems. The achieved results refer to the substantial benefits related to potential energy savings thanks to the decreased temperature peaks, caused by phase change materials (PCMs) that act as a medium with the ability to absorb or release thermal energy according to ambient temperature [7; 8; 9]. In particular, the application of PCMs in climate zones with noticeable diurnal temperature swings may be viewed as an advisable strategy. As reported by Refs. [10; 11; 12], distinct energy savings can be obtained with the help of the incorporation of PCMs into building elements such as walls, floors, and roofs. On the other hand, the utilization of PCMs is accompanied by several critical issues, including the limited mechanical performance, leakage of PCMs, subcooling phenomena, and the limited range of the phase change [13; 14]. The type and applied dosage of PCM in building composites have been questioned by several researchers, since the equilibrium between satisfactory mechanical performance and thermal storage capacity needs to be described [15; 16; 17; 18]. Further improvements related to the mentioned PCM drawbacks have been subjected to comprehensive research, and a detailed understanding of the outdoor climatic conditions and indoor requirements can be found in several studies and review papers [19; 20; 21]. Besides the heat transfer, the moisture transport and storage properties of porous building materials have a significant effect on energy efficiency as well. This phenomenon was studied in detail for typical building materials such as bricks, aerated concrete, plasters, and insulation materials in particular to provide insight into the interaction between water content and thermal performance [22; 23; 24]. As revealed, the effect of moisture content could result in a substantial deterioration of thermal insulation capability [25; 26]. In other words, the moisture-related issues require significant attention, and the neglect of the correlation between moisture and heat transfer may result in very unpleasant consequences [27; 28; 29]. Namely, undesirable levels of indoor moisture may cause considerable health issues, such as asthma, allergies, skin or eye irritation, etc. The aforementioned issues further increase the importance of the complex assessment and control of indoor air quality, taking into account both the thermal and moisture buffering of building materials in order to prevent the risk of Sick Building Syndrome [30] or other unpleasant consequences. The moisture buffering performance is usually described by the help of the moisture buffer value (MBV), which refers to the capability of the applied finishing building materials to respond to moisture loads, thus balancing the excessive or too-low levels of relative humidity [31; 32].