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Official Journal of the Japan Wood Research Society

Predicting the humidity control capacity of material based on a linear excitation-response relationship


The Cb value is a useful parameter for estimating the humidity control capacity of materials. It is defined as the ratio of the range of variation of relative humidity in a steel box lined with the material of interest to that in an empty steel box, when sinusoidal temperature variation is applied. However, because it takes a long time to obtain the Cb values for materials at each temperature variation period, we developed an easier method based on a linear excitation-response theory to obtain the Cb values without measuring at each period. Japanese cedar was the material used in this study. The temperature excitation, a jump from a constant temperature to another constant temperature, was used to obtain the absolute humidity response. Under the assumption that the temperature excitation-humidity response relationship is linear, we were able to predict humidity variation to sinusoidal temperature variation at any period, and we obtained the Cb value for each temperature variation period. Predicted values agreed well with the experimental values. From this, it was found that the Cb value could be predicted without measuring the Cb value at each period over a long time. In addition, the peak time difference, which is closely related to the Cb value, could also be predicted in a similar manner.


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Correspondence to Toshiro Morooka.

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Morooka, T., Homma, Y. & Norimoto, M. Predicting the humidity control capacity of material based on a linear excitation-response relationship. J Wood Sci 53, 199–203 (2007).

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Key words

  • Humidity control capacity
  • B value
  • Cb value
  • Japanese cedar
  • Linear excitation-response theory