I have a closet in my office that I'm using as a server room in my house. As I add more equipment in there, it generates a significant amount of heat, which is contributed to by the office itself (which has two computers).

My living room, on the other hand, with a seldom-used fireplace and large older window (both issues I plan to address in the future), tends to get very cold in the winter (US/Massachusetts).

It seems to me the obvious solution would be to put a small fan in the ceiling of the closet (where convection will naturally carry most of the heat), and put a duct in the attic crawlspace that exhausts into the living room. It may not contribute a whole lot of heat to the (much larger) living room, but if I can drop the office temperature by 2-3 degrees and raise the living room temperature even half a degree or so, it'd reduce the temperature gradient just a wee bit and maybe said gradient wouldn't be quite so noticeable when I leave the office and go into the living room.

Is there any reason I shouldn't do this? Please note that my primary concern is eliminating heat from the closet (as we all hopefully know, electronics don't really like getting too hot). Reducing temperature in the office would just be a happy side effect, and I figure dumping the heat into the living room is more efficient than just dumping it outside since I've already paid for the electricity that produced it.

EDITED for diagram and additional info:

Below is a diagram of the relevant areas. I'd like to avoid having the air blow on the armchair area (there are actually two along that wall)... I would like to vent the hot air more or less into the center of the room so it's not blowing on anyone who's seated. I was thinking a louvered vent above the sofa's front edge (about 2-3 feet in from the wall), pointing inward to the room, would dump the heat into the living room without creating drafts for anyone in the seating areas.

Floor plan

  • And what will you do in the hot season? – Ecnerwal Mar 29 '17 at 1:33
  • @Ecnerwal I'll figure it out. We don't have central cooling of any sort, and the office can't accommodate any reasonably-sized window AC (whereas the living room and kitchen can), so pumping the excess heat in the office out to the area where the AC is -- and theoretically sucking return air from that cooler end of the house -- should still help maintain more even temperatures. That's my theory anyways, unless I'm still missing pieces to this puzzle? – Doktor J Mar 29 '17 at 3:56

There is no code against ventilating your closet into the other room. There are all kinds of crazy things I have seen to take a room that has great ventilation and move it to another room. If you go in the south of France you will see fans between the living space that has outdoor access in the connecting rooms.

The only issue becomes if you had toxic fumes (which you wouldn't in another interior room) and this is common with a work area or garage (cars).

As far as going through the attic well attic fans exhaust attic air into your living space and attic air probably isn't as clean as the other air you are breathing as attics often have mold, dirt, and open insulation. You are just tunneling through using appropriate piping which should be metal ducting or PVC.

Let me tell you why what you are doing is a good idea - since we should all look to make our houses energy optimal - but very flawed at the same time. It is flawed because during the periods of the year that are cold and you want the next room warm you will be going through a cold attic. The output of whatever your server generate is no way a furnace, the ducts will get cold and you will end up spitting out cold attic temperature air to the next room. The fact is the fan plus cold air will cost you energy money.

Really you want to just vent right to the attic when it is warm out. When it is cold out you want to vent right to the other room. You could do this with decorative grating/cover between the rooms and possibly the use of a fan in the grate itself. There are probably a lot of unique ways to create airflow between the rooms, with pipe/duct being an option but not an efficient one as it will not necessarily capture all of the heat and if it does will require a lot of power from a fan. Nothing wrong with using a fan but it shouldn't need to be on all the time and shouldn't need to require that much force.

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    Unfortunately the kitchen pantry sits between that closet and the living room, and I don't care to heat the pantry. Perhaps I can either run the ducting through the pantry along the ceiling, or insulate the ducting as it runs through the attic? Ideally I'd rather the "exhaust" be more central in the living room as we have seating around the edges (see edited-in diagram)... – Doktor J Mar 28 '17 at 22:32
  • Either you need to switch the pantry around with the closet or you just let it escape to office and put something where office air can escape to living space. Ducts will help push air to attic during warm season but I don't thing you are going to gain efficiency by using a blower. I used to run rather large labs at my company. We had building efficiency experts come in and we just vented out of the room with heavy AC. The thing is the equipment gets warm but the area is only warm because the air doesn't escape. It isn't that warm in general. How many servers do you have? – DMoore Apr 5 '17 at 15:06
  • Well switching isn't an option. Right now it's just my cable modem and a pfSense router box... but I'm preparing to install my NAS, which is a tiny beast with nine 5TB hard drives, and once the NAS is done I will be putting in a print (and more) server as well (we have a large-format photo printer, laser printer, scanner, and 3D printer that will all be attached to it). – Doktor J Apr 5 '17 at 18:14

Excellent idea. We do that (move "waste heat") in commercial buildings. However, be careful to: 1) verify no smells are being transferred, 2) make-up air is provided to the computer room, 3) transfer duct is insulated so not to loose all the heat out the duct, 4) keep transfer duct on "room side" of insulation envelope, and 5) don't let the transfer duct's grille blow heat on living room's thermostat...or any thermostat.

1): Smells can come from the closet or adjoining office. Be aware of what's left in the room. We found cleaning supplies in a computer room once when a client complained.

2): Make up air is important because your fan can push the air if it can't get more air to come into the room. Maybe provide a duct from the living room for the make-up air.

3): If the distance is very great, you'll loose all the heat out the duct before it gets to your living room. Consider adding duct insulation.

4): An easy way to transfer most of the heat is to keep the duct on the room side of the insulation. Maybe consider running the duct in the attic rather than crawl space where it's easier to move the attic insulation on top of the duct.

5): Make sure the transfer duct grille does not blow on the living room's thermostat. We like to locate grills by windows to temper the colder air you often find there and eliminate condensation. However, now with thermal pane windows that's not so important anymore. By the way, you may want to locate the thermostat that turns the computer closet fan on, in the closet...not in the living room.

One side benefit is keeping your computers cooler so they run better.

Note: The only Code issue you have to worry about in a residence is the wall between the garage and the house. You can't penetrate it without a 1-hour fire damper.

  • 1) The closet is already open to the office (and my desk is about 2-3 feet from the closet doorway), so unless I haven't showered I don't think there will be any objectionable smells getting sucked in ;) – Doktor J Mar 29 '17 at 3:47
  • 2) Due to the elevated temperature of the office, the door is pretty much always open. Hopefully this would help in promoting air circulation so cooler air from the living room end of the house (the kitchen is usually cooler too) comes back toward the warmer end (the bedrooms tend to be warmer as well) – Doktor J Mar 29 '17 at 3:48
  • 3) Insulation is definitely a thing. Might double-walled ducting be worth the cost, i.e. put the air duct inside an oversized duct and fill the space between with insulation? – Doktor J Mar 29 '17 at 3:50
  • 4) We don't have a separate attic, just the crawlspace above the ceiling... I don't think the current insulation up there goes above the rafters, so I'd be running the duct over that insulation (since it has to go over the rafters) and then installing additional insulation over the duct. – Doktor J Mar 29 '17 at 3:52
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    I think you might want to look at a low volume fan like they use in a greenhouse attached to a house. It doesn't cost much to run and it's set to come on when the greenhouse is hot and uncomfortable. You may be able to add a thermostat in the living room and tie it to the thermostat in the closet. Then, the fan would come on when the thermostat in the living room calls for heat AND the thermostat in the closet says it's warm enough in the closet to transfer (exhaust) heat. – Lee Sam Mar 29 '17 at 4:07

I would consider adding a bank of fans, (3) 6" fans maybe, mounted in the wall above the sofa as close to the ceiling as possible. They would pull air from the office into the living room. Then add a bank of fans at the top of the closet wall to pull air from the closet into the office. I would also add a normal ceiling vent fan like used in a bathroom in the top of the closet to vent heat into the attic during warm months.

Use movable louvered grates over the exhaust side of the fans so air can be directed to fall closer or farther from the wall as desired.

Since hot air rises, if you can draw the warm air exiting the closet, across the office ceiling and into the living room fast enough, you'll get some benefit In the living room. Otherwise, the office will just stay toasty.

The loss of warm air into the office due to it starting to fall as it cools could be eliminated by later adding an in-room duct along the ceiling from the closet fans to the living room fans if necessary. Curve it if possible so it's more stylish and moves air easier.

Note that turning on a ceiling fan in the office would direct all the closet heat into the office instead. None would reach the living room unless it's ducted.

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