- Jun 10, 2014
- Reaction score
Thats a different material. Polystyrene versus polyisocyanurate that is used in PIR solid insulation board.My polystyrene cups in the 90s seemed to keep my coffee pretty hot without the foil backing, but as I say, I am certainly no expert.
(my personal solution was to not drill at all into the keezer and run 3/16 inch tubing through lid, just cracked open, with silicon to seal it up nicely.)