Does the sleeved part of the post become saturated with water?

Not at all. In a typical post, water enters from the ground, increasing the moisture content of the wood to a level at which decay can start (>25%). When a Polesaver-PF Sleeve is applied, it seals the critical ground-line surface of the post, significantly lowering the entry point of moisture from the ground.

While moisture can still evaporate from the above-ground section, the moisture content in the upper-sleeved part of the post is kept much lower than in an unsleeved post. This reduction in moisture helps prevent decay and rot, ensuring that the post remains protected and durable for many years.