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In the summer the main floor with the AC is always comfortable, the basement is a bit warmer and the 2nd floor unbearably hot.

I'll be adding more insulation under the roof to help, but short of getting a mini-split or central air unit, I'd like to explore circulation options to help spread the cool air from the main floor to the basement and 2nd floor.

I have a 40 x 30 ft, 1945 home... basement, main and second floor, all finished. Heat is supplied via gas furnace, hot water circulation to all three floors. There are no air registers, duct work or openings between floors, the stairwells have doors on them.

There is one 14,000 BTU wall AC unit on the main floor that cools the entire floor, no trouble at all. It's mainly open concept with over 50% of the entire space open. The basement and 2nd floor are completely open, one room each.

My first thought is to install two vertical ducts on opposite sides of the house that run from top of the 2nd floor to the bottom of the basement, a fan in each, with an adjustable vent on each floor. The vents would be at the ceiling level of the 2nd floor and floor level on the main and basement. The fans would run in opposite directions when the AC is on.

Would this work? Am I missing anything important? I'm aware of the potential fire hazard when air is allowed free movement between floors.

I attached a photo of what I'm thinking. "AC" is main floor, "Warm" is basement" and "Hot" is 2nd floor. Air flow, register placement and fans are designated.

home diagram

Thanks for any advice! Brian

  • 2
    Are you absolutely sure your AC has the extra capacity to cool more volume? Unless it's significantly underloaded now, you'll get 2 hot floors at best. Top floors receive much heat through roof, so they need much more cooling than lower rooms to begin with. – Agent_L Apr 17 at 10:11
  • @Agent_L Good point. It would be a shame to do all that work and not have capacity. Adding another AC to the main floor at that point would just be silly. Maybe put a portable or wall unit on the 2nd floor and circulate the main and basement air. That would still be cheaper than a mini-split or central air. If I WAS sure of capacity I hope my air flow concept is at least sound! Thank you! – Brian Apr 17 at 18:56

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