Well, I would start out small with 8 stalls and eventually make a bigger barn. This barn is almost EXACTLY my dream barn but mine would have 12x14 stalls, dutch doors leading out of stalls into runs and the hay room would be a big tack and equipment area 2012 Barn Pics
And if I lived somewhere where it dropped below 0 F I would want it to be heated, not overly, just to prevent it from freezing- wouldn't have to bring liquid supplements inside. Lots of big doors and everything luxury for horses! Horsey treadmills, hot-walkers, you name it! And, plenty of turnout, everyone would have big 100 foot runs and be turned out for at least 8 hours a day in winter in 2+ acre grass turnouts with other horsey buddies. In summer turned out all but the hottest hours in which they would be brought into the cool barn. To keep the barn cool there would be misters and those huge industrial fans overhead plus little fans by each stall... getting a little carried away!