The room may be small. The heat load inside it may not be.
Originally published October 14, 2013. Updated October 2026.
IT closet cooling can become a surprisingly persistent problem after occupancy, even though the room itself may be one of the smallest spaces on an office project.
Servers, switches, UPS equipment and other electronics generate heat continuously. Put enough equipment into a small enclosed room and the temperature can rise quickly—even when the surrounding office is comfortable.
Then someone asks the seemingly simple question:
Do we need a fan, or do we need supplemental air conditioning?
That is usually the wrong place to start.
The first question should be:
How much heat are we actually putting into the room, and how is the design removing it?
Start With the Equipment Load
An IT closet should not be treated like an ordinary storage room.
Before deciding how to cool it, the team needs to understand what equipment will be installed, its anticipated electrical load, operating hours and how much heat it will reject into the space.
That information should be coordinated among the IT team, electrical engineer and mechanical engineer.
This is especially important because the equipment list can change during a project. A room originally planned for a few network switches may eventually contain UPS equipment, additional racks or other hardware that significantly increases the heat load.
The cooling strategy designed for the original equipment may no longer be adequate.
A Fan and Air Conditioning Solve Different Problems
Ventilation can move heat out of a room, but it does not create cooling.
If the surrounding space is cool enough and the heat load is modest, transferring air may be sufficient. That could involve a transfer grille, exhaust arrangement or another engineered ventilation solution.
But that approach depends on where the heat is going.
Dumping warm air into a ceiling plenum or adjacent space without understanding the building HVAC system can simply move the problem somewhere else.
When the equipment load is greater, the room operates beyond normal building HVAC hours, or temperature control is critical, dedicated cooling may be appropriate.
The answer comes from the load and operating requirements—not from the size of the closet.
Do Not Forget After-Hours Operation
This is where office projects can get caught.
The building’s main HVAC system may maintain comfortable temperatures during occupied hours. IT equipment may operate 24 hours a day.
What happens at 2:00 a.m. when the building air conditioning shuts down?
The same question applies on weekends and holidays.
A cooling strategy that depends entirely on the base-building system needs to account for that operating schedule.
The room does not stop generating heat because the office is closed.
Coordinate It Before Construction
The worst time to discover an IT closet cooling problem is after the racks are installed and operating.
Adding dedicated cooling later may require electrical capacity, condensate drainage, controls, refrigerant piping, roof or exterior access, landlord approval, and changes to ceilings or finished construction.
What looked like a small mechanical issue can become an expensive retrofit.
During design, confirm the anticipated equipment load with IT and have the mechanical engineer document how that heat will be handled under both occupied and unoccupied conditions.
Then revisit the assumption if the equipment changes.
Small Room. Real Design Requirement.
An IT closet may occupy only a few square feet on the plan, but its operating requirements can be very different from the rooms around it.
Don’t begin with:
“Should we put a fan in there?”
Begin with:
“What is the heat load, when is it generated, and where is that heat going?”
Once those questions are answered, the appropriate cooling strategy becomes much clearer.
Leadership takeaway: Treat IT-room cooling as an equipment and operating requirement during design. Confirm the load, hours of operation and heat-removal strategy before construction makes the solution expensive.
About the Author: Richard Neuman advises organizations on capital planning, project governance, and complex capital programs. He has overseen more than $2 billion in capital investments across commercial real estate, healthcare, utilities, industrial, broadcast, and development projects.
He writes candidly from an owner-side perspective about the executive decisions and organizational dynamics that shape capital project outcomes.
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We are just building in an offices TI an IT room and are solving the HVAC with 2 – 1.5 Tons InRow units to operate 24/7 and backed up with a generator. Units system is new for me, they take the heat to the plenum and are mounted at side of racks.
The units are produce by American Power Conversion.
Put a supplementary A/C unit in the closet and minimize your risk factor.
Mission Critical?
Perhaps this is overkill, but some of my clients have wanted to keep the equipment operating and cool even when the central air conditioning is down. In that case we have simply located a thru-wall window A/C unit above the IT closet door, and pumped the excess heat to the corridor or corridor ceiling.
We have also on a few occasions supplied that A/C unit with backup generator power. If your VOIP or phone system lives in that room (as it typically will), you should seriously consider supporting its operation even when the central A/C is down.
Fantastic article
!
Thank you everyone for your kind comments, feedback and contribution.
Richard Neuman
Excellent, well researched and thoughtful article, particularly the forumulas. Thank you. This info needs to carry through to the architects, so they can pass it through on plans! Codes vary as to municipality and sometimes you can/can’t have louvered doors, for one example. Pushing solution off on tenants is poor end-strategy, for long term relations as well.
So very true… I have done many T.I. projects where the IT equipment is in a cabinet… No ventilation whatsoever… I always suggest to the tenant to move this equipment into a ventilated storage room with a dedicated space… In other words, make sure they don’t pile boxes or other items that would block the equipment and restrict air flow… Good article…
Note by Ron Dickson–
When you consider the critical importance of the IT gear, it would be foolish to trust its safety to a single exhaust fan. It would be better to install a second fan on a dedicated electrical circuit and with its own thermostat. If the primary fan fails, the back-up fan should come on automatically. This should also turn on a warning light at the receptionist’s desk or other highly visible place.
Great article and so very true!!!