Does anyone know a cheap and efficient way to lightproof and insulate a window. I was thinking of drawing the shades to a close while leaving the window open. Then tacking up a sheet over it and finally screwing in a piece of styrofoam board or sheetrock over that. The window will also be my exit for my exhaust so I would cut a whole out of the board or sheetrock, of course. Any advice greatly apprecciated.