The barn where I ride (Virginia, USA) is built like that, and it has great air flow. The horses get fresher, cleaner air to breathe than they would if they were completely inside. We get pretty mild weather here, usually not over 100 degrees F in the summer and it usually doesn’t snow in the winter, a few inches at the most if it does. There is an overhang on the barn so the horses are protected from heat/cold when grooming and tacking up. We have a separate hay barn which is better just because of fire hazards as the main barn is wooden. If you want to be able to cross tie, here we have small pillars/poles in front of the stalls where we can cross tie or tie. I find the shed row style a lot more convenient than indoor because there is lots of space to bring horses through without someone being in the middle of the aisle. The only con is that we don’t have any indoor grooming spaces, but if it’s too cold to groom then it’s too cold to ride.