Air-drying is one of the most frequently used operations to dehydrate logging residues for production of wood fuel chips. This study developed a drying curve model for the air-drying of logs in order to estimate drying time to reach a given moisture level, and to evaluate the influence of log properties on drying characteristics of logs. Log piles of sugi (Cryptomeria japonica) were air-dried in Tsukuba city, Japan, from November 2014 to August 2015. A hierarchical Bayesian model was used to estimate the moisture content of individual logs as a function of initial moisture content, diameter, length, heartwood ratio, and drying time. The measured mean moisture content fit well to the estimated drying curve, indicating that the developed model is a potentially useful method to estimate the drying time for any moisture content within the limited range of climate conditions studied here. A comprehensive evaluation of log properties affecting the drying characteristics of logs showed that initial moisture content, diameter, and length have an influence on the drying rate of logs.

In Shiiba Village, Miyazaki Prefecture, people have used many trees growing in their living area for their traditional life. We interviewed four elder informants who were expert in wood handling on wood physical and mechanical properties and durability in commonly used trees. The informants discriminated 99 tree species empirically and evaluated their toughness, cleavability, warping, checking, abrasion resistance, hardness, machinability, combustibility and durability. Overall the highest rated species were Torreya nucifera and Sciadopitys verticillata, and the next-best species were Taxus cuspidata and Zelkova serrata. On average, coniferous species were evaluated better than hardwood species, and in hardwood, the arbor trees were evaluated better than shrubs. Air-dry density from previous literature was correlated with empirical toughness, machinability, cleavability, hardness, abrasion resistance and combustibility. Brinell hardness in the literature was correlated with empirical hardness, and decay resistance in the literature was correlated with empirical wood decay and termite resistance.

The change over time of the indoor air quality of a special elderly nursing home made of wood was investigated. The direct measurement of indoor air revealed that the main component was terpenes, a known source of woody aromas. The contribution of each part of the woody interior to the quality of the indoor air was investigated using an emission test cell method. The results showed that α-Pinene, the main component of the detected terpenes, was emitted from Hinoki timber used for the post and brace, and that sesquiterpenes (α-Muurolene, Calamenene, δ-Cadinene, etc.), which counted for 10-40% of the detected aroma, were emitted from the sugi lumber used for flooring and roof sheathing. A year after construction, the concentrations of some sesquiterpenes, including Calamenene, which is a source of woody aromas, had increased although the total amount of terpenes had decreased. Consequently, it was found that of the indoor air components the woody aroma mainly derives from terpenes.

Walking is an essential part of life or work and causes floor vibrations. Recently, the need for large-scale wooden buildings has been increasing. However, there is no guide to design for floor vibrations caused by walking of large-span wooden floors. Therefore we considered the relationship between vertical vibration and properties of wooden school and office floors and human sensory evaluation. We found that the percentage of persons indicating perception of vibration, expecting those who answered unnoticed, was larger than the perception probability indicated in Guideline for the evaluation of habitability to building vibration published by Architectural Institute of Japan (AIJ). When the floor response acceleration was over 4 cm/s², the percentage of persons who perceived the vibration was 100%. At the next step, we considered the relationship between the weighted acceleration level according to frequencies and the ratio of deflections including creep to spans, calculated by the experimental stiffness. Finally we suggest a tentative design target for large-span wooden floor as follows. In order to get the weighted acceleration level to be 65 dB, we must set the ratio of beam deflections including creep to span at less than 1/500 according to Building Standards Law and at less than 1/600 according to Standard for Structural Design of Timber Structures by AIJ. We also must set the floor natural frequency to be over 12 Hz. These values are available under the condition that the natural frequency of wooden floors is from 9.5 Hz to 12.5 Hz.