# Characterization of Responsive Plasters for Passive Moisture and Temperature Control
## Materials and Methods
### Experimental Methods
The device operates on the basis of a dynamic measurement principle that enables multiple measurements thanks to a reduced measurement period. The water sorptivity properties were obtained from the water absorption experiment. Here, the studied samples were insulated from lateral sides to maintain one-dimensional transport, hung on automatic balances connected to the datalogger, and immersed a few millimeters under the water level. The mass change was recorded, thus the water absorption coefficient is defined as  
\[A=\frac{i}{\sqrt{t}} \tag{1}\]  
where \(i\) (kg/m\({}^{2}\)) is the cumulative water absorption and \(t\) (s) is the measurement period. Consequently, the moisture diffusivity \(\kappa_{app}\) (m\({}^{2}\)/s) was given by the following formula  
\[\kappa_{app}=\left(\frac{A}{w_{sat}\ -\ w_{0}}\right)^{2} \tag{2}\]  
where \(w_{\text{sat}}\) (kg/m\({}^{3}\)) is the saturated moisture content and \(w_{0}\) (kg/m\({}^{3}\)) the moisture content of the dry sample. The water vapor transmission properties were determined on the basis of the dry cup method arrangement. Five samples with a circular cross-section of 100 mm and a thickness of about 25 mm were used. The sealed cups were placed in a controlled climate chamber (\(t\) = 21 \({}^{\circ}\)C, RH = 50%) and weighed periodically. To increase the accuracy of the measurement, combined temperature/relative humidity probes (Ahlborn, Holzkirchen, Germany) were placed in the cup for monitoring RH development. The achieved values of mass gain were used for the calculation of the water vapor transmission properties according to the following equation  
\[\delta=\frac{\Delta m\cdot d}{S\cdot\tau\cdot\Delta p_{p}} \tag{3}\]  
\(\Delta m\) (kg) is the change in sample mass due to water vapor gains diffused through the sample, \(d\) (m) is the sample thickness, \(S\) (m\({}^{2}\)) the specimen surface, \(\tau\) (s) the duration of the experiment relevant to mass change, and \(\Delta p_{p}\) (Pa) the difference between partial water vapor pressure in the climatic chamber and in the cup with the silica gel. Afterward, the water vapor diffusion coefficient \(D\) (m\({}^{2}\)/s) and water vapor diffusion resistance factor \(\mu\) (-) were calculated by using Equations (4) and (5)  
\[D=\frac{\delta\cdot R\cdot T}{M} \tag{4}\]  
\[\mu=\frac{D_{a}}{D} \tag{5}\]  
\(R\) (J/(K-mol) is the universal gas constant, \(M\) (kg/mol) the molar mass of water, \(T\) (K) the absolute temperature, and \(D_{a}\) (m\({}^{2}\)/s) the diffusion coefficient of water vapor in the air. The expanded uncertainty of the measurement was 3.3%. Sorption and desorption isotherms were obtained by using a dynamic DVS-Advantage vapor sorption device (Surface Measurement Systems, London, UK) to get mass gains/loss at 20, 40, 60, 80, and 95% RH. A DVS-Advantage device was operating in dm/dt to define the equilibrium point. The dm/dt value of 0.00004%/min was applied for all replicates. Three samples of each material were measured due to the time-consuming measuring scheme. The hysteresis of the sorption isotherms was calculated from the obtained sorption and desorption curves. The moisture buffering of the developed plasters was studied due to its contribution to the passive moderation of indoor relative humidity levels according to the approach suggested by [PERSON] et al. [44]. Samples with know surfaces were exposed to cyclic moisture loading at a given temperature (21 \({}^{\circ}\)C). For this purpose, a dynamic DVS-Advantage vapor sorption device was set to maintain cycles of 70% RH for 16 h and 30% RH for 8 h. The mass gain/loss was recorded for 5 complete cycles (=120 h). Consequently, the moisture buffer value (MBV) was calculated as the maximum moisture uptake per 8 h of absorption cycle considering the selected RH gradient of 40%. The relative uncertainty of the measurement was 4.0%.