Keep it closed up and open once in a while for a day or 2 to air out if you don't use it for an extended period. If left open in your barn, the open windows and doors on the barn will allow dust, dirt and pollen to blow in and accumulate on the fabric and through the screens. Not to mention birds perching on top of tent material along with the associated mess. Did I forget to mention mice dropping off the rafters and making or finding a way in through the fabric especially where it wraps around the bunk edges. Don't forget to mouse proof the underside.