A.Corresponding editor Paul Fisette responds: If the relative humidity is in fact 100 percent, then of course there will be no drying. However, since the relative humidity is not 100 percent all the time, some drying will occur during these periods.

Remember, the rain screen provides you with insurance. The siding keeps most of the liquid water out of your wall system, and the screen provides backup protection. The air space allows any water that gets past the siding to drain, and the circulating air helps dry the back of the siding and the wall when they get wet.

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