A venting question... want to put rack in utility closet

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New Member
Dec 5, 2014
Bought a new house and i'm getting it wired up. In my previous place we had an attached garage so I ran all the wires there and that was just fine for all my equipment. In our new place I'd *like* to put it in our utility closet or, failing that, in an under-the-stairs closet or maybe in my media room (the first is way more preferable).

My concern is, that's where the hot water heater is (on-demand with a small storage tank and the feeds for in-floor radiant heating) as well as a "heat return" unit (I guess this is a Canadian thing... never heard of it when living in the states). I've gotta put a temp probe in there to really measure but I'm guessing the ambient temp gets up to 80F. Each of those units *does* have their own venting system.

So, working on the assumption I need to do something about this... just mulling my options. I could set up vents to the outside if I needed to (the rack would be on an outside wall). Would prefer to not have that expense though. I'm worried that just putting bottom pull and top push fans in would not be sufficient. Putting vents on the utility room's door out into the house (as others have done here with their closets) is probably not gonna work

Any thoughts/experiences to share?


Active Member
Apr 4, 2011
I would be worried about electronics next to things that create heat and hold water. That being said, I am building a dedicated closet for some of my equipment that doesn't have an exterior wall. For venting I am going with a mini split AC unit.
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Active Member
Jan 22, 2019
I personally would advise against putting anything of serious value into a tight place surrounded by any form of water system. (sods law has a nasty habit of paying us a visit, a told you so moment)

Attic crawl space?
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Active Member
Jan 18, 2017
You'd need a split system a/c or some other form of cooling, even a couple of servers and a switch in an enclosed space will get too hot. The water is also a concern.


Post Liker and Deal Hunter Extraordinaire!
Jul 21, 2017
As others have mentioned, water and heat are bad.

But to the point of what you're trying to do, depending on what type of active venting there is, you may just have to beef that up for the additional btus from the servers. Or if those systems have some sort of pwm feature, just set them to 100% and see how much cooler the room becomes.

That heat return line sounds like part of a hot water re-circulatory system which effectively means you've got a radiant heating system in that room as well.

As far as the water and temp concerns, you can always monitor the server temps, but you could also install a vertiv geist setup so you can monitor the room temps and humidity. I just finished a project with their products and was nicely impressed. In fact, I was just noticing how the humidity was showing an uptick since the site has had rain for the last few days.

Sean Ho

Nov 19, 2019
Vancouver, BC
The air return can be a good thing. If you have a heat recovery ventilator, you can duct your server exhaust to its indoor air return. During the heating season (presumably, most of the year in Canada), heat from the server exhaust together with heat from other return air will help to pre-heat fresh outside air, lessening the load on your heater core. Intake for the servers would be from the house (during the heating season) or an outside fresh air intake (during the cooling season).


Feb 26, 2021
I have my setup in a closet, although no water heater or HVAC. I have a blower that blows air in the bottom of the closet and then a vent that allows the air to exit. During the summer I vent the air to the HVAC room which is on the other side of the wall. During winter, I vent the air into my office space, and it helps to heat it (and I closet the HVAC) vent.

Works well for me and only about 10W of power consumption.


The New James Dean
Jul 27, 2015
Others have said everything...

I'd like to speak to the "Under the Stairs" scenario - as this is exactly what I did a few years ago. I had to go the 1/2 rack route though (the DIY 20U plans online). But I only need 14U. Anything else is just a bonus for spacing.

I was lucky enough that the bottom of our stairs are almost enclosed. Meaning, heat generated in the back will "rise up" along the bottom of the stairs to where the top landing meets the rafters. Also, our stairs are in a very large foyer that is very large and has ample room to dissipate any heat being exhausted.

So, I've cut a hole in the drywall above the door and put a normal looking A/C return-vent shield I picked up from a local hardware store. Behind it I have two large 240mm (yeah, big) fans that are quiet.

Option 1: The door itself currently has a 2" gap under it (I've removed all flooring, tile, etc - to remodel) so that should be enough to feed fresh air.

If Option 1 doesn't work out once the floor is installed, Option 2 is that I can easily poke a hole into the stairwell and pull in fresh air from beside the cabinet - down low - using another A/C return-looking vent.

The overall concept is NOT to vent into the crawlspace/attic because any "venting" means you have to re-supply the air back into your house somehow. (and I have a whole re-cycling system design going in soon for that, don't need a server closet screwing with those CFMs)

Bonus is that any heat generated warms the foyer, which in the area I live needs a little heat 8 months of the year. Being in Canada, I'd imagine you're in the same boat.