Our kitchen includes three sources of heat – radiators, a wood stove, and the cook stove – and a staircase that provides a convective pathway to the second floor of our house. I wanted to stop warm air from the kitchen from flowing up those stairs. We didn’t want to reinstall a door that once been there and a blanket we had used one year was problematic for an older resident of the house. The solution was a slat door made two layers of 60 mil polyethylene film cut in strips about 5″ wide, overlapped with the cuts staggered such that the cut in one layer is covered by a strip of the other.
I sandwiched the slats between two halves of a dowel that I slit in half and mounted the dowel on curtain-rod cups.