Slightly OT: Calculating HVAC requirements for server rooms

Frank Bulk frnkblk at
Sat May 2 08:28:15 CDT 2009

And when he writes "professional", that might mean someone with more
expertise than your average commercial HVAC shop.  I've seen it countless
times where general contractors do a great job on almost every aspect of the
building but fail miserably when it comes to setting aside space for network
equipment and remembering to cool that gear in the IMF rooms.  Those
experiences have put me on the offensive when working with such folk -- you
literally have to stake out your ground and remind them of the cooling needs
every step along the way.


-----Original Message-----
From: Ricky Beam [mailto:jfbeam at] 
Sent: Friday, May 01, 2009 11:06 PM
Subject: Re: Slightly OT: Calculating HVAC requirements for server rooms

On Fri, 01 May 2009 21:32:19 -0400, William Warren  
<hescominsoon at> wrote:
>> Specifically, I am using the guide posted at:

"Before you decide on an air conditioning unit you should commission an  
audit from a suitably qualified air conditioning equipment specialist or  

Translation: Hire a f***ing professional.

And that's exactly what you need to do.  Qualified HVAC installers (with  
specific data center experience) will know far more than us "network  
types" will ever want to know about cooling.  They do this for a living,  
and thus, know all the tiny details and odd edge cases to look for. (like  
looking above the drop ceiling -- that's what it's called, btw -- and  
seeing what's up there long before pencil meets paper (not that anyone  
uses paper anymore.))

> You also have to take into account the environment surrounding the data  
> room.  At my wife's work The ceiling above is only separated with a  
> false ceiling to the metal roof above but the rest of hte spaces  
> surrounding the room are climate controled.  They [had] to significantly  
> upsize to account for the heat load of that ceiling.

Unless you are pulling air through the plenum (that space above the drop  
ceiling), the air up there shouldn't matter much -- there should be plenum  
returns up there to begin with venting the air to the surrounding  
plenum(s) (i.e. the rest of the office, hallway, neighboring office,  
etc.)  However, I've seen more than enough office setups where the  
"engineers" planning the space completely ignore the plenum.  In my  
current office building the static pressure pushes the bathroom doors open  
by almost 2".  And they placed our server room directly under the building  
air handlers -- meaning all the air on the 3rd floor eventually passes  
through the plenum above my servers. (also, the sprinkler system riser  
room is in there.)

Bottom line, again, ask a professional.  NANOG is a bunch of network geeks  
(in theory.)  I'd be surprised if there's even one licensed HVAC "geek" on  
the list. ('tho I'm sure many may *know* an HVAC engineer.)


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