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Venting a server closet or A/V closet in your home or small business is really simple, and it is something builders should include when they build your home. Even just a switch or two can bring an unventilated closet well over 110 degrees. This is bad news for your home and the equipment!
Before we talk about venting a server closet the right way, I want to share with you my situation. When we built the home, I originally had just a small router from Verizon FiOS in the room and a 24 port PoE switch for my cameras, and a really crappy D-Link NVR that I wouldn’t recommend to my enemies. In addition, this closet houses all of the cabling and switching for my home theater room. The server closet is about 4ft by 6ft, and it would stay about 90 degrees in this room at all times. Something I felt was reasonable.
Over time, I upgraded the equipment in this room pretty significantly. I added a wall-mount rack (see that project here), an additional 50 port PoE switch, two Core i7 1U Servers (see my project How to Build a 1U Server), a Synology NVR216 for recording my IP Cameras, a Synology Rackstation RS2416+ NAS/iSCSI, two rack-mount 1500KVA UPS, and finally a small pfSense firewall appliance (hands down the best firewall you can get, and its open source).
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You may think that all of this is a lot of stuff that’s not really needed, and to some degree you are right, but just a single server, UPS, and switch are going to generate enough heat that the room should be vented. As you can imagine the heat generated in this room became so much that I had to start leaving the door open to keep the equipment from overheating. This compounded the problem. Computer equipment makes a lot of noise, and that noise was now diminishing the enjoyment of my theater room. I needed a solution.
Before we go on, I want to clarify what I mean by venting. We’re not interesting in supplying more air to the room. The builder installed an A/C vent to this room during construction. This is fine, but it will never solve the problem and could actually make things worse.
First of all, when the A/C is running you will make headway due to the cold air being injected into the room. That makes sense, right? The hot air will be pushed out under the gap at the bottom of the door, just like any other room. However, when the A/C is not running heat is continuing to build and if its a mild day outside, the A/C may never run at all. This means no venting will ever happen. Bad news.
But it gets worse! In the winter months you will be injecting hot air into the room compounding the problem! What we need to do is exhaust the warm air from the room, not inject air.
To solve for exhausting this heat, I took a two pronged approach. The first is that I installed a return air vent in the server closet ducted to the return air side of the home A/C unit. That alone will make a huge difference, but it won’t solve the problem. There will still be days that the A/C (or furnace) will never run. To solve for this I installed a continuous blower into the ducting for this room. This fan will pull about 25 watts and continuously exhaust air from the room, even when the A/C or Furnace is idle.
Even though the fan is designed to be installed either at the return vent, or at the A/C unit by default, I opted to install the blower about three to four feet from the rooms return air vent inline with the ductwork. I chose this location for one simple reason. It reduces the noise of the fan to point where it is almost silent. If you place the fan directly at the room return it will make considerable noise.
Additionally, I added a variable speed controller between the fan and the outlet to allow me to adjust the airflow of the fan should I ever want to slow it down, or simply turn it off. I finished off the install by spraying insulating foam into all of the gaps and cracks round the new return vent. I plugged the fan into the same outlet used for the furnace. This means the maintenance switch will disable this fan in addition to the A/C and furnace when working on the system.
The results far exceeded my expectations! Before adding this additional powered return my server closet would overheat and my equipment would start sending out warnings within half an hour. Temperatures would rise to 110 degrees and eventually equipment would start turning itself off to prevent damage.
With the powered duct vent installed, the room maintains at about 80 to 85 degrees. More than acceptable for my purposes! If you had more equipment you could step everything up to 8″, or with less you might be able to step down to 4″ versions of everything.
If you’d like to vent your server or A/V closet efficiently and not for much money I’ll provide links to everything I used below.
Update 08/15/2019: This solution has now been running for a little over three years and continues to exceed my expectations for venting my server closet. Not only that, I have significantly increased the amount of gear in this closet over that time. I’ve added another disk array, another server, lots of home automation goodies, etc. The room stays at a consitent temperature even when its well over 100° degrees outside (roughly 38° C).
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21 Responses
I don’t know why this isn’t the #1 site on the internet. This is something I have been hoping to figure out how to solve for a long time and could never find any decent information about how to accomplish it. My home theater closet is a sauna and I’ve been afraid my amplifiers were going to catch fire or die an early death. THANK YOU for this!
This is how I vented my AV closet. It works perfect. I can tell you right now that you should be careful with these fans. They do eventually fail after many years of use and then your closet will overheat. The best way to handle this is to make sure you have a temperature probe on one your PCs and have it alert you if something fails.
Agreed! I have two monitors in the closet. One is Observium which monitors via SNMP. I also have ZWave probe from my home automation system in there.
How are you getting air into the room? Vented door?
All interior doors have a two inch gap between them and the floor for exactly this purpose. Standard home construction.
Hi Mike. Your article is a godsend! I am hoping you might have a few more great thoughts on this scenario: my server closet will be connected to a soundproofed home theater room and although the closet door will have an air gap at the bottom, there will be no gap under the theater room door. The theater room door will have weather stripping around the sides and a self-sealing automatic door bottom. Will the air pressure in the theater room and the closet equalize automatically by having air flow into the theater room via the supply register then under the closet door and back into the closet return register? And if so what can I expect the temperature of the constant draft to be (will it be attic temperature, closet air temperature, or something else)?
Makes sense. I’m going to be doing something similar with my mining closet. With my two 8 GPU mining rigs, things quickly became very toasty in there. Quick question. Since you have the exhaust pumping into the return side of the air handler, I’m guessing the hot air gets circulated back into the house when the A/C isn’t running? Possibly helps heat the house in the winter?
Great Article! This is exactly the setup I was looking for. Forgive me for the very basic question, but what is the order of installation? I’m trying to find out how the fan is mounted and connected to everything. Also, would it be possible to just let it vent in to the attic and not connect to the return? I’m hesitant to cut into any of my existing hvac. Thanks again!
Not connecting it to your AC would cause a lot of issues and would be against code in most countries. You’d just be blowing all of your air conditioning into the attic like leaving your front door open 24/7.
I run my duct with a splitter.
In the winter, it goes into the cold air return line, and in the summer it goes outside.
It’s just under the limit for needing make up air, but prevents me from having to cool the air through my A/C unit like I believe yours would.
I actually considered that, but there’s a an issue I didn’t like. When venting air to the outside you’re causing negative pressure in the home. For air to leave the house, new air must enter the home. This means it’s being pulled through cracks in your doors, etc. Pulling in outside pollens and the like. I didn’t want that.
4.5
Thanks for this, exactly the guidance I was looking for.
Nice setup, but now your server closet is truly a plenum space connected to your home’s air distribution. Aircraft do this with smoke detectors and automatic valves that can either vent air overboard or forced closed loop ventilation, and pilots always have the option of breathing bottled oxygen, and someone is always awake monitoring things. But you have the option of just stepping outside so yay for being on the ground and not needing 7 to 8 psid in the house all the time. You’re probably safe to sleep if you used all plenum rated stuff. BTW, I have a Honeywell wifi thermostat that can run the furnace/ac fan independent of heat/cool modes.
Hey Mike! Time for me to upgrade from my towers to some rack mount gear so I’ll be insulating and ducting a closet for use….. hope the db stay within acceptable ranges
You didn’t specifically mention it but I assume you’re manually closing the HVAC vent when the heater starts running consistently with cooler/cold weather? Otherwise you’d have 100-110 deg heat blown in coupled with the 100-110 deg heat from your equipment? Or do you not worry about that since the heater only runs for a finite amount of time as it cycles on and off (non-heat pump) and the duct fan will catch up shortly after the furnace shuts off?
I don’t worry about it all… The duct fan removes the air so quickly it just doesn’t matter. Barely a blip on my environmental monitor.
I am trying to solve a similar problem. My equipment is in a media rack (computer server rack) in my home theater. It cools fine. Also, most of the equipment (Game console, projector, AV receiver, etc.) is powered off unless we are in there.
Given that our thermostat is in another part of the home, the room heats up before the AC cycles back on. We have extra AC ducts, so it cools down quicker/lower as well. We are cycling between being too hot and burying ourselves under blankets.
I feel like, if I could vent the heat above the media rack, that it will reduce the temperature swings.
The fan would be in my attic, though. And I really do not need it running all the time. I was trying to find some kind of remote thermostat to activate the fan/ No luck yet. If I could implement your design, but with the addition of a thermostat I think I would be in business. It seems like it could also help you/others, if your equipment is not running all the time.
Craig
Can you elaborate on your wifi thermostat? I am trying to get my FAN to run via a remote temperature sensor to balance the temperature in my Home Theater.
Not being very handy I have tried to hire someone to do this for me with no luck. The HVAC/Ducting people won’t touch such a “small” job and handymen don’t want to cut into the insulated ducts. My server closet is in the loft (above an uninsulated garage) and right next to the fireplace chimney. As it is I had to put in a 12K BTU window AC in the loft b/c to keep the loft cool I was freezing out the rest of the house. I have a 14×14 air return in the wall next to the closet and right above that an AC register.
I’m guessing is that maybe I should just vent the closet into the loft (30×24 with 10′ ceilings) and hope for the best.
I am interested in trying this out in my closet. I am not sure I can run the return duct all the way back to the main unit, but can connect it into an existing return duct. Can I cut that duct, and add a “Y” connect to splice this run into that?