## 3 Methods  
### Experimental Design  
For each specimen the change in weight of the specimens was investigated, when subjected to triangular or sinusoidal simultaneous temperature and RH variations. Specimens were tested in an environmental chamber (ACS Compact Test Chambers DY110), into which a mass balance were placed to continuously measure the change in weight, as shown in Figure 1. More details of the set-up can be seen in [8] The tests followed the general guidelines for humidity variations and test set-up of the NORDTEST protocol [14]. The materials were exposed before each tests to 24 h pre-conditioning at 23 \({}^{\circ}\)C and 54%RH, and to six cyclic humidity and temperature variations at an air speed of 0.1 m/s. Each cycle consisted of humidity variations from 75%RH (high RH) to 33%RH (low RH), and temperature fluctuations between 18.0 \({}^{\circ}\)C and 28.0 \({}^{\circ}\)C, which is the acceptable operating temperatures in buildings in the ASHRAE Standard 55 [22]. Temperature was set to follow inverse variation than RH, as shown in Figures 2 and 3. For both triangular and sinusoidal fluctuation, three different humidification and de-humidification time intervals were defined, as shown in Table 2.  
Figure 2: Triangular temperature and RH variations, **(a)** Triangular 12/12 h; **(b)** Triangular 8/16 h; **(c)** Triangular 72/72.  
Figure 3: Sinusoidal temperature and RH fluctuations, **(a)** Sinusoidal 12/12 h; **(b)** Sinusoidal 8/16 h; **(c)** Sinusoidal 72/72.  
In the _Triangular 12/12_ and _Sinusoidal 12/12 tests_, considering 54%RH as starting point, the positive section of the curve represents the humidification phase, while the section below 54% is the de-humidification interval. As with the NORDTEST [14], the RH was gradually increased, until reaching its maximum 75%RH and then back to 54%RH. In the first 6 h of the de-humidification from 54%RH the humidity reached the minimum 33%RH, and then again up to 54%RH, as shown in Figures 2a and 3a. In the _12/12_ test, the climatic chamber increased and decreased the RH every hour, transitioning from one step to the other by setting a \"slope\", which the climatic chamber automatically generated, to progressively increase/decrease the humidity until the next RH was achieved. In the _Triangular 12/12_, the triangular curve shape was generated by creating 24 equally distributed RH intervals, while the _Sinusoidal 12/12_ was achieved, by constructing a sinusoidal symmetrical equation. The temperature curve followed the same logic as the RH variations. In _12/12_ test the curve started at 23 \({}^{\circ}\)C, reaching the minimum temperature of 18.0 \({}^{\circ}\)C within the first 6 hours of the cycle. Successively, the temperature jumped back to 23 \({}^{\circ}\)C, to increase the temperature to 28.0 \({}^{\circ}\)C always withing the 24 h cycle. In the _Triangular 8/16_ (Figure 2b) and the _Sinusoidal 8/16_ (Figure 3b) the temperature and RH curves were marked by hourly interval in the humidification/cooling phase and by 2 h intervals in the de-humidification/heating phase. The _Triangular 72/72_ (Figure 2c) and _Sinusoidal 72/72_ (Figure 3c) follow the same principle of the 12/12 h fluctuations, but 6 h intervals were applied between one step and the other, in order to understand if slower moisture variations influence the sorption capacity of the materials. A temperature and RH sensor for each specimen (Tiny Tag TV 4505) monitored the climate condition in the climatic chamber to observe the agreement between the target fluctuations and the actual measurements on both sides of the chamber. The accuracy of the sensor was \(\pm\)0.5 \({}^{\circ}\)C for the temperature and \(\pm\)3%RH for humidity.