Of all the cardboard costumes I've seen, very few people address just how hot it can get wearing one of these. Cardboard is an excellent insulator. This can work in your favor or against you. To make it work for you, finding a way to keep the temperature inside the costume cool is crucial, and not as hard as it might seem. A little goes a long way. To keep the temperature inside manageable, I used chemical ice packs. They not only get instantly cool, but you can avoid the condensation mess, and because you are in a insulated box, the cooler temperatures go a long way. In addition to the chemical ice packs, I have two personal battery fans that are fastened with velcro on the inside of the costume. The cold air from the ice pack would get recirculated into the costume through the fans. The ice pack cost $4, and I got the fans from Amazon.com for $12 a piece.