I have a server room about 12 feet square with an unfinished ceiling (exposed ducts and wiring). It houses a few servers (about ten, 1U and 2U) and some networking gear (four 1U switches, three routers, three modems, two cable boxes).

With the door closed, it runs around 80 degrees Fahrenheit with half the servers turned on. When I turned on all the servers it reached 86 before I chickened out and propped the door open.

The room is adjacent to air-conditioned office space, but does not itself have dedicated air conditioning. The ventilation for this room seems to be limited to one duct coming in at ceiling level, with a powered fan to draw air in, and one duct at ceiling level to allow air to flow out (it seems like it may just go into the drop ceiling cavity in the adjacent room).

The adjacent office space stays fairly cool, but I'd prefer not to leave the door propped open all the time.

There is both 110v and 208v service in the room, and plenty of power available. But there are no windows, and no floor drains (in a pinch we might be able to run a condensation hose through a small hole we'd drill in the wall to a nearby sink area, but only if absolutely necessary).

I've considered portable A/C units, but I'm not sure on sizing and a lot less sure how we would run the exhaust hose(s). I suppose we could point one at the existing room exhaust duct (air return), but substantially modifying the duct is probably a no-no.

I've also considered installing a fan box in the door of the room, but I'm concerned that this will only drop the temperature a little. Even right now, with all the equipment on, the room is at 83 degrees with the door open. And the main building A/C turns off daily at 6 PM to conserve energy, so the adjacent room temperature rises at night.

How would you cool this room? Let's say the goal is to bring the temperature with everything running from a steady state of around 90 degrees down to 75 (equivalently, to offset the heat produced by ten 1U servers).