My main living room has a 25 foot cathedral ceiling with a ceiling fan including a staircase going to the second story bedrooms. The thermostat is situated in this space.

There is space to install a vent and ducts to move air from this ceiling hot zone to the first floor main bedroom. I would like to create a system that has:

  1. Has two temperature probes - one in a the "hot" area and the other in the "cold" area.
  2. Controller which will detect if there is a "Max" difference between the hot and cold zone,
  3. Start the fan in the new duct which will stop when the second "Min" temperature difference between the hot and cold zone is reached.

Is there something like this commercially available or do I have to cobble it together myself with a 1-wire system or multiple thermostats?

4 Answers 4


I suspect this will be a DIY project.

Note that an alternative would be to simply install ceiling fans in the cathedral ceiling room to circulate its air better, removing most of the stratification you now experience.

(I've got upstairs/downstairs zones myself, with definite air exchange at the stairwell. I've considered installing a vertical tube with a boxer fan or two to get some counterflow there. Simpler alternative might simply to be to close the doors of the upstairs rooms, or to install a door at the landing, to limit the airflow.)

  • 1
    +1 I don't disagree with any of your comments. I really would like to move the hot air to another part of the house instead of just "stirring" it around in the one room. Ideally I would want to circulate it down to the basement but I have no clear paths to install a vent. Some of it can be achieved by "balancing" the vents and closing doors. I also have a gas fireplace in the great room which heats it up, leaves the top bedrooms to warm and the main floor bedroom "cool"
    – gwallis
    Commented Nov 22, 2014 at 21:04
  • It's certainly an interesting question, and a plausible suggestion. I'll be interested to hear if you can make this work.
    – keshlam
    Commented Nov 22, 2014 at 21:47

I had to construct my own solution with a new duct line using an inline 720 CFM Inline Fan, 8-Inch sitting in the attic.

A Samsung SmartThings IOT (Zigby) system was used to monitor temperatures and turn the fan on. A motion sensor with built in temperature was installed at each ducting endpoint. A smart wall switch was used to drive the fan. I could manually turn the fan or drive it with SmartThings custom smart controller.

I created own SmartThings controller to monitor temperatures in the two rooms to switch the fan on when the temperature delta is over a certain value.

Worked OK but attic fan was a little loud and a mild winter this year made it somewhat redundant.


My father in law got some flexible ducting, maybe 6" in diameter or more and hooked a fan to it on the intake side that blows air into the pipe. He has a "Sun Room" that gets pretty warm, and it funnels the air into the house in the winter. He heats with a wood burner in the basement so it's a big deal to use the extra heat source.

Sounds like you want to rig something like that up. I can get more details on the fan he used if you care, but I'm betting it's not rocket science to set something up.

  • Thanks - I've looked at them and I understand how to do it. You can get an in duct fan which will move the air. I would like to have that automated which will require two thermostats linked to the fan. Some of the newer home automation tools will allow you to rig this up but they are fairly expensive.
    – gwallis
    Commented Jan 28, 2015 at 20:21

A thermostat like this could do the trick for you, just wire it to something like a bathroom vent fan in the ceiling.

Then run some duct work or flexible tubing into the HVAC duct system where you want it to go (or optionally just add a vent somewhere for the air to come out)

A fan that size can be very quiet which is good and the throughput of a small fan is low enough that you could probably get away with 2" flex tubing so it could go pretty much anywhere.

Only drawback it this system wouldn't give you your two location temperature reading.

You could likely wire two of them up (and at 15 bucks a piece getting two isn't a big deal) and feed them both to an electronic switch at the fan, but that complexity of wiring is beyond me so I am not sure how it would work.

There are also multi-zone thermostats you could check out. Not terribly familiar with them but it may be an avenue for you to research at least.

Edit: Ok I was curious so I went out and looked some things up...if you are willing to spend more time an money a system like this (scroll to the What Zoned Temperature Control is and why you need it section) would solve this problem nicely.

I am not recommending that particular product mind you, I have no experience with it, but the explanation of what Multi zone is and how it works is useful.

  • Another drawback is that hiding the insulated ductwork may be a challenge
    – keshlam
    Commented Jul 24, 2015 at 19:52

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