We wet them down for 3 reasons, to pack them down so they do not just end up on the edges, to keep them from blowing all over and or out of the trailer, it does help keep the trailer cooler if it is hot out. We do not soak them to the point they won't adsorb, just so they pack down, if it is hot and dry out they will dry out pretty fast from the air flowing through the trailer. I should add we try and use a heavier shaving, the real fine shavings do not work as well, and if not packed down, your trailer will look like a pop corn popper with the lid off as you go down the road.