## 3 Results and Discussion
### Observation of RH Changes  
RH of indoor air not only affects occupants' thermal comfort but also plays a key role in a building's energy consumption. Wood exposed to indoor environments absorbs moisture when the relative humidity rises, and conversely releases stored moisture into the air when the humidity drops [16; 17]. The moisture buffer capacity of the wall-covering materials, as well as furniture and textiles inside the buildings, define the hygroscopic inertia level of a room, which can play an important role in the reduction in RH peaks. In terms of RH variation, the building with a 90% wood interior composition showed a monthly average that was 5.2% lower (77.3% \(\rightarrow\) 72.1%) than the non-wood building during the humid summer month of August, and 10.9% higher (25.4% \(\rightarrow\) 36.3%) during the dry winter month of January (Figure 3). The wood coverage at the 45% coverage one exhibited a humidity control performance comparable to that of the 90% coverage one under moderate humidity conditions (40-60%). The difference in the average relative humidity between 45% and 90% in intermediate humidity conditions was less than 1%, which was smaller than the difference in humidity between 0% and 45%, which was 2-3%. However, under low and high humidity conditions, its performance was similar to that of the 0% wood coverage. Wood is a natural hygroscopic material that is mainly composed of cellulose, hemicelluloses, and lignin. The water adsorption capacity of the amorphous part of cellulose is similar to that of hemicellulose, where an increase in crystallinity decreases the moisture adsorption capacity [18] ([PERSON] et al., 2022). It has the characteristic of trying to balance the temperature and humidity changes in the air. When the humidity in the air is high, it absorbs moisture, and, when the humidity in the air is low, it releases moisture. As a result, it showed contrasting results in summer when the humidity is high and winter when the humidity is low. For example, hygroscopic building materials can absorb moisture in a high humidity environment and desorb it in a low humidity environment, and, thus, they can adjust the indoor relative humidity without energy consumption. It is essential that we maintain the indoor humidity environment steady within an acceptable range of 40-70% [19]. This indicates that wooden indoors contribute to controlling the indoor humidity levels close to the optimal range for human comfort, even without additional humidity control equipment. From June 2021 to January 2022, the measurement results showed significant changes in the equilibrium moisture contents and RH values in indoor environments based on the degree of wood coverage. In the outdoor environment, EMC showed large fluctuations due to the significant seasonal changes in temperature and humidity. In contrast, indoor EMC varied according to the degree of wood coverage: in August, the 90% condition showed an approximately 2% lower EMC compared to the 0% condition, while, in January, it was approximately 2% higher. Thus, a higher degree of wood coverage was associated with \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Factors**} & \multirow{2}{*}{**Measurement Range \({}^{*}\)**} & \multicolumn{5}{c}{**Degree of Wood Coverage (\%)**} \\ \cline{3-8}  & & **0** & & **45** & & **90** \\ \hline Benzene (\(\mu\)g/m\({}^{3}\)) & 30 & 4.3 & 7.4 & 6.2 & 3.9 & 5.2 & 4.0 \\ Toluene (\(\mu\)g/m\({}^{3}\)) & 1000 & 34.5 & 37.2 & 36.1 & 22.4 & 33.8 & 26.1 \\ Ethylbenzene (\(\mu\)g/m\({}^{3}\)) & 360 & 5.7 & 6.5 & 6.4 & 5.5 & 7.2 & 5.6 \\ Xylene (\(\mu\)g/m\({}^{3}\)) & 700 & 9.6 & 8.4 & 11.6 & 10.7 & 14.8 & 12.1 \\ Styrene (\(\mu\)g/m\({}^{3}\)) & 300 & 1.5 & 3.9 & 2.7 & 0.9 & 2.1 & 1.3 \\ \hline \hline \end{tabular} \({}^{*}\) Thresholds stipulated in the IAQ Control Act by the Korean Ministry of Environment.  
\end{table} 
Table 2: Mean values of BTEXS in wooden and non-wooden environments. increased moisture absorption, resulting in lower EMC values (0%: 13.2, 45%: 13.9, and 90%: 11.5).