How to maintain relative humidity in a wooden structure?

The wood is adjusting to the surrounding temperature and moisture levels, thus the structure of it may alter as a result of variable moisture levels.

When discussing how a dehumidification system should be designed for a wooden structure in order to control the RH%, the following two points are critical:

1) What should the humidity setpoint be to achieve x% water content in the wood?

This question can be answered if you know the moisture equilibrium curves (moisture sorption isotherms) for the material in question. From such curves, we will know where to aim at the humidity setpoint.

2) How can we best manage the area of air that needs treatment?

This question requires some insights on the construction itself: How tight is the construction (how much air will leak)? How big is the area of dehumidification? Are there any other air handling systems in the area to consider? and so on.