Ideally a bi-directional through-wall vent + fan would be great with built in thermostats measuring both sides.

I haven't found that nor am I entirely sure what to search for. Are there components that I could buy that provide this functionality?

So all fans AFAIK are bi-directional components. The issue is the controller and I don't care about controlling speed as much as the direction + on/off.

One solution I have in mind is something like this:

[through-wall fan/vent system] -> [some sort of inline polarity switcher] -> [wall plugin thermostat controlled relay]

The issue is the polarity switcher. A manual polarity switch would be fine since I'd only maybe need to change it seasonally for the most part. What can I look for that does that?

PS: I am not looking to cut anymore than a single whole in the wall (and no more than 4-9" diameter) and simple set up is a plus. Long term I may loop back and do a custom job with an arduino but for now I'm looking for cheap, easy & off-the-shelf.

  • Could you back up and describe the situation?
    – iLikeDirt
    Oct 14, 2014 at 0:11
  • Two rooms with different temperatures side by side. One room is presently generating excess heat that could be better used elsewhere in the house.
    – Enigma
    Oct 14, 2014 at 0:13
  • Like a server room or something?
    – iLikeDirt
    Oct 14, 2014 at 0:31
  • Yeah essentially.
    – Enigma
    Oct 14, 2014 at 1:32

3 Answers 3


Simply exchanging the air between the rooms will equalize the temperatures because the air will mix. I would just cut two vents in the wall, one high and one low. Natural airflow probably won't be enough to balance the temperature, so put a fan in one or both of the vents. If you do both, point the fans in opposite directions.

Again, it doesn't really matter which way the air moves because it will mix.


Here's a dead-simple idea: use a PTAC unit to air condition the room with excess heat, and dump it into the adjacent room.

That's the general idea behind how companies with huge server rooms recycle heat during wintertime. Their systems are much more sophisticated, of course, inevitably involving heat exchangers, water cooling, thermostats, multiple zones for the heat so conditioned areas don't get too hot, etc.

There are many other ways to do this, depending on the details of your house. If you have ducted heat, you could rig up an air or water-based heat exchanger attached to a new coil in your HVAC air handler. If you have hydronic heat, you could use a similar heat exchanger to put the heat into that system. Etc. It's probably beyond the scope of this website to design such a system for you, but hopefully I've given you some ideas. There are many ways to move heat from one place to another. Get creative!


I am not aware of any professional products for this, but you could get an arduino or rasberry pi device with two temperature sensors, and hook it up to a bi-directional fan and write some code to have it automatically start at a certain temperature difference.

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