Depending on how much heat your equipment is producing, your building codes, and where you are getting your fresh air from, then you might have to vent the heated air out of the building. The principal still stays the same though, cooled air (cooled by your HVAC) in from the front (that's why those servers have fans sucking air in) and heated air out the back. Some form of top mounted fan or back door unit to suck that hot air and blow it out (via some ducting) out of the building if it's a lot of hot air, or up in the plenum space which would then vent out the building through normal means (again, check your building codes in your state) if the heated air is minimal.
Again, it's all about controlling that air flow. The construction of "most" enclosures are built for that purpose. The side panels, the front filler panels, fan kits, etc... are all there to ensure proper air flow so that heated air is directed out of the cabinet. What you do with it once it's made it out of the cabinet is then your responsibility. But I can tell you, the servers do not want that heated air circulating in same room and your HVAC system will never be able to cool that hot zone until you get rid of the hot air.