Wood, as a natural material that stores carbon, is gaining increasing attention and has potential for use in interior architectural applications. Given the long indoor stay time characteristic of modern society, it is important to scientifically understand the effects of indoor wood application on the occupants. In this study, three residential buildings with an identical area and structure were constructed with different degrees of wood coverage (0%, 45%, 90%) using Larix kaempferi. Subsequently, indoor air quality (IAQ) evaluations and relative humidity measurements were conducted to assess the physical and chemical changes in each environment. The IAQ in wooden and non-wooden environments met the recommended IAQ standards established in South Korea. The results of the 8-month observation showed that, the higher the wood coverage ratio, the more the indoor humidity fluctuations were alleviated, and, in the case of the 90% wood coverage ratio condition, the humidity was maintained 5.2% lower in the summer and 10.9% higher in the winter compared to the 0% condition. To further assess the physiological responses induced by the wooden environment, the heart rate variability (HRV) was measured and compared for 26 participants exposed to each environment for two hours. In environments with a 0% and 90% degree of wood coverage, no statistically significant differences were found in the participants’ HRV indicators. But, in the group exposed to the 45% wooden environment, the results showed an increase in HRV indicators, natural logarithm of high frequency power (lnHF): 4.87 → 5.40 (p < 0.05), and standard deviation of normal-to-normal intervals (SDNN): 30.57 → 38.48 (p < 0.05), which are known indicators of parasympathetic nervous system activation.

Total volatile organic compounds (TVOCs) are widely used to assess indoor air quality (IAQ). However, because TVOCs combine diverse compounds into a single metric, they cannot distinguish individual emission sources or chemical characteristics. Indoor environments with natural materials such as wood may emit biogenic volatile organic compounds (BVOCs), elevating TVOC concentrations and limiting the interpretation of indoor air quality. This study evaluated TVOC concentrations and chemical composition before and after installing wooden interiors in 36 public facilities in South Korea, including daycare centers, nursing homes, and welfare facilities. Domestic wood species, including Chamaecyparis obtusa, Larix kaempferi, and Cryptomeria japonica, cover approximately 49% of the interior surfaces. Major regulated VOCs, including benzene and toluene, did not increase significantly after installing wooden interior materials. Mean TVOC concentrations increased from 244.2 ± 139 to 640.1 ± 542.3 μg/m³, accompanied by significant increases in several terpene-related BVOCs, including α-pinene, myrcene, and cymene, as well as an increase in the absolute concentration of unidentified VOCs. Elevated TVOC concentrations in wood-based indoor environments may reflect compositional changes rather than poorer indoor air quality. Therefore, TVOC concentrations should be interpreted alongside compound-specific analyses rather than relying solely on a single TVOC indicator.