Regarding keeping a server room cool: on the low end, there's box fans. On the high end, there are architectural changes to the building.

What are some practical ways to keep the room cool without resorting to either of these extremes?

  • Box fans will RAISE the temperature (not lower it) unless they can draw cooler air from outside the building or another room that maintains a consistently lower temperature than the server room itself. – Tall Jeff May 3 '09 at 15:56
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    True, but if there is a heat problem in the server room, there almost certainly is another room that's consistently cooler. – Richard Gadsden May 8 '09 at 9:29

Turn unneeded servers off!

I know it sounds obvious, but I've seen numerous servers left on for no reason, or because people weren't sure they were being used!

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    Suspend to RAM so you can boot them up rapidly (seconds rather than minutes) if need be. – Adam Gibbins May 2 '09 at 23:10
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    Windows Servers mostly won't hibernate, though, and I know I wouldn't trust a server to come out of suspend. – Richard Gadsden May 8 '09 at 9:28

To add to the advice of "Turn unneeded servers off!" is virtualization. The best way to control heat is to eliminate it. If multiple server can be consolidated into fewer servers, less power is consumed and less heat is produced.


Make sure you've got the hot and cold aisles right with the air flow configured properly. It'll help the servers a lot if you haven't done that.

Without resorting to architectural changes, we've used portable air conditioners in addition to large fans for times when we were doing structural work (like swapping out UPS systems).


Portable air-conditioning units where you just hang a heat-exchanger out of a window work well for a short-term solution until you can get something designed-in.

  • Was going to post the same thing; for such a simple solution, this can work wonders. – Richard Morgan Apr 30 '09 at 12:32
  • I've had success with portable air conditioners. Only thing to watch out for is needing to empty condensation water from the system. – Mike H Apr 30 '09 at 12:39
  • Very inefficient though, not to mention expensive. I can hardly lecture on this though as we currently have four on lease with their discharge hoses poked through a hole in the drywall following a spate of unexplained hardware failures, assumed due to excess heat. – Lunatik May 7 '09 at 20:50

At the low end:

  • Fans in a closed space are not going to work, as it will just circulate the heat rather than removing it.
  • Ventalation fans providing fresh air can help when there is a suitable place to pull air in and push air out to.
  • A small free standing or surface mount air conditioner will work well for small server rooms and comms cabinets, you will need to make sure they are placed in such a position that the air can circulate. They also require somewhere to vent the heat out to.

At the high end:

  • Get someone in to do a survey and do the calculations for you, it is easy to spend a fortune on something that is either going to be way over the top, or not sufficent.

My favorite was: open the windows.

I was working with a company whose server room was on the first floor in a very well ventilated corner of a building, and they kept complaining about the server room getting too hot despite the air-conditioning.

Turned out that opening the window dropped the temperatures to below 25C for most of the year, and below 20C most of the winter.

Of course there was really good airflow in and out of the room, so I guess it's an exceptional case.

  • In an emergency, by all means open a window, but even as a short term solution it has some pretty serious issues. 1) Moisture, even in a dry western climate humidity from a passing storm can be really bad news. 2) Temp consistency: you may not believe it but expansion/contraction from varying temperature can cause problems on some boards and even force cards out of slots (there's a reason CPUs and memory slots have those ridiculously tight fits and latches). – JRS Sep 7 '15 at 20:54

You can go with a spot type air conditioner such as units like these. These units are self contained and only require a water supply and drain to remove the heat and therefore don't require architectural modification for ducting, etc...only a plumbing hookup. You don't even need to pressure balance the room because the air is completely recirculating. Relative to cost, I believe they are both cheaper to acquire and also more efficient than the more typical air flow based condenser units because the water is better at removing heat from the coils than air.

If you are concerned about the water consumption, for some added cost the water can be recirculated via pipes to an outside radiator to dump off the heat before bringing it back around.

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