If I were you, I would port holes in that entire piece of PVC pipe and then add an outer shell (larger piece of PVC pipe).
Afterwords, stuff some sort of insulator in between the the ported "barrel" and the "outter shell."
Two excellent insulators that I tend to use are fiberglass (As in the pink fiberglass used to insulate some of the older homes) and egg carton foam.
You can also use tissue paper, carboard, cloth, etc.
However, egg carton foam or fiberglass work the best.
-Brian
