How long is the cable between the two buildings? How good is the wiring between the buildings? Personally I'd chuck the hub and get another switch. Remember that a switch resets the maximum distance for copper, but a hub doesn't. Not to mention it would totally route-isolate both buildings. Right now the hub has to rebroadcast everything across the long run. If you had 2 switches, only true cross-building traffic would be transmitted over the long run. Less chance for collisions, too.