The fan doesn't fit into a normal energy star approved window in a new home without major modifications. It comes with screws that would suggest the manufacturer wants you to screw it into your window frame (if it fits). We were not about to ruin our window (and you cannot close the window if you screw in the fan. Making a cheap plastic fan a permanent part of your window is probably not the intention of most buyers. The plastic wings that pull out to accommodate different sized windows has a circle cut-out that allows air from outside to come in... as well as bugs and rain. This is a very confusing design. Why would you want a hole in your fan? We attempted to use it twice despite it's ill-fit, but it's motor was too powerful and blasted it out onto the tile floor below. The second time it happened, it broke. Waste of money.