Turn on the fan and watch as it inflates! Depending on your entrance size, it will stay inflated. If it doesn't puff up very much, the scrunch up so...
I tried this out after seeing Summer Igloo by Instructables user fungus amungus. I changed some things around, but all credit goes to him for the idea.
Step 1: Materials
For this project you will need: a few jumbo garbage bags (6 in this case), some tape, some heavy objects, and a box fan. Note that a sheet will work in place of the garbage bags. Although since we wanted it to be larger, the sheet was not big enough.