Uneven Cooling (Heat Rises)

I have a 3 story townhouse which is too warm upstairs or too cool downstairs. I have tried keeping doors closed upstairs, covering vents downstairs, etc. but degree diff is still about 5 per floor (basement 70, main 75, top 80. I have a heat pump with auto thermostat but no zones and apparently no dampers.
Any experience or thoughts about a separate duct and fan (Not part of the heatpump ducts) just to TRY to recirculate air between the top floor and the basement? Would this idea actually work? I have a 12x20 master bedroom and a 15x20 basement office room that could be connected by a duct (6" to 10"? wide) by about 25' long (mostly verticle) with two 90 degree turns. Should the fan blow air up from basement or down from bedroom or does it matter?

 

[RJVAN]

If you don't have A/C, put exhaust fans in the top floor ceiling or windows, and open your basement windows so the cooler air is sucked upward while the warmer air is blown outside. (If you put in an automatic exhaust fan, make sure it has a high-temperature cut-out switch to prevent the spread of a fire.)

If you do have A/C, why not duct most/all of the conditioned air to the third floor, and let nature take its course. Of course, you might need to add a booster fan to your ductwork.

 

[ChasBean1]

culver -

I like your idea but also like RJ's response. If you're set on this type of configuration and for this to work, you'd need two ducts - one with a fan to recirculate the air and one to provide a transfer pathway back to the source. Gut instinct tells me to advise you to put the fan in the duct that sucks from the high floor and discharges to the basement. If it sucked from the basement and discharged to the high floor, making the basement become negatively pressurized would tend to draw out radon and soil gases. It might also cause problems (e.g., death) by starving combustion sources within the basement.

As a side note, sucking air from the top floor should be from a source across the room from the return transfer duct.

Another thing - if the basement space isn't tight, much of your fan flow will leak into unwanted areas... For this reason, it might behoove you to install a very slightly smaller fan in the riser back to the top floor...

(Thinking out loud at the moment). Those are some of my first thoughts. Best of luck, -CB