## 4 Results  
### Experimental Results  
The moisture buffering performance of clay and gypsum under triangular and sinusoidal temperature and RH fluctuations is shown in Table 3. The average peak to peak sorption capacity was calculated by considering the last three cycle of the 12 h and 8 h, as the changed in weight stabilised after the third cycle in all tests. In general, gypsum had a better moisture capacity than clay (Figures 4 and 5), by adsorbing two times more moisture regardless of the shape and time interval of the temperature and RH fluctuations. The performance of gypsum is due to its porosity and pore structure. As explained in [8], gypsum presented higher porosity than clay, but it also showed a significant presence of micro-pores that increased themoisture uptake of the material. Differences between the 12 h and 8 h curves in the triangular case either for clay and gypsum were negligible, as the same moisture uptake was measured. Between the _Sinusoidal 12/12_ and _Sinusoidal 8/16_ curves 11% and 5% variations were observed for clay and gypsum, respectively. However, differences were small and not significant, when compared to the differences between triangular and sinusoidal sorption responses. There was 18% and 20% differences between _Triangular 12/12_ and _Sinusoidal 12/12_ peak to peak sorption capacity, while between _Triangular 8/16_ and _Sinusoidal 8/16_ clay and gypsum presented 10% and 13% variations, respectively. The _Triangular 72/72_ and _Sinusoidal 72/72_ tests presented the most significant discrepancy, as clay and gypsum adsorbed 20% and 26% more in the sinusoidal case,respectively. The considerable higher sorption capacity of the 72/72 tests is related to the longer time interval, which allowed materials to adsorb more water. Figure 4: Moisture uptake curves for clay and gypsum under triangular temperature and RH variations, (**a**) Triangular 12/12 h; (**b**) Triangular 8/16 h; (**c**) Triangular 72/72. \begin{table}
\begin{tabular}{l l l c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{**Curve**} & \multicolumn{4}{c}{**Sorption [g/m\({}^{2}\)]**} \\ \cline{3-5}  & & **12 h** & **8 h** & **72/72** \\ \hline \multirow{2}{*}{Clay} & Tri & 26.69 & 26.33 & 76.34 \\  & Sine & 32.77 & 29.36 & 95.69 \\ \hline \multirow{2}{*}{Gypsum} & Tri & 59.83 & 60.38 & 142.69 \\  & Sine & 72.25 & 68.47 & 181.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Sorption capacity of clay and gypsum (peak to peak) for the triangular and sinusoidal temperature and RH variations. Figure 5: Moisture uptake curves for clay and gypsum under sinusoidal temperature and RH fluctuations, (**a**) Sinusoidal 12/12 h; (**b**) Sinusoidal 8/16 h; (**c**) Sinusoidal 72/72. As [8] also mentioned in a study on sinusoidal environmental variations, the triangular and sinusoidal curves presented a delayed response to the temperature and RH fluctuations (Figure 6). The hygric lag varied depending on the humidification and de-humidification intervals, the length of each step, the material's characteristic, but especially on the simultaneous temperature variations. Table 4 summarises the hygric lags in all the tests, where the first value represents the time between the RH-peak and the moisture uptake peak, while the second represents the time between the lowest RH and the lowest moisture uptake value. In the Triangular and Sinusoidal 12/12 clay and gypsum showed different lags, in which clay always presented a slower response than gypsum either in the adsorption and desorption. Regardless of the materials differences, both plasters showed an asymmetry between the humidification and de-humidification. The desorption lag was 30 min for clay, and 20 and 60 min for gypsum in the _Triangular 12/12_ and _Sinusoidal 12/12_, respectively. The asymmetry indicated that in the de-humidification the response of the plasters is quicker than the adsorption, probably due to the effect of the air movement in the chamber that slowed the humidity uptake and increase the moisture release.