The bedroom on the third floor of my house has floor one floor vent for supply and one for return. In the summer, the central AC works extra hard but yet the bedroom is only about 75% cool compared to the rest of the house. I reckon the cold air coming out of the single supply vent flows along the floor without rising to the bed level and pours out of the bedroom down the stairwell into the house below. I say this because there is quite the pressure gradient between the second floor and the top of the stairwell on the third floor since its really hot in that stair well. All the hot air from the house is collecting there.

I am going to block the bottom of the bedroom door with towels or put weather strips. But I wanted to know if I can run a makeshift duct from the floor vent to the ceiling of the bedroom so that the cold air at least cools the room as it rushes toward the stairwell instead of flowing along the floor. It wont be pretty and it will be visible, but that is something I can live with.

What materials would I need to properly cover the vent and run a duct to the ceiling? I would appreciate any insight to this matter. Thank You


Bedroom Schematic

I have added a schematic diagram of the room with dimensions including the dimension of the vent which is 12 inches x 6 inches. The height of the room is 12 feet. I guess I have more of a fluid dynamics question now. Whether I use register boosters or duct guides, is it realistic to expect the dense cold air to fan out as it heads to the floor? Or would it just stream back to the floor in a columnar fashion?

  • you could use this ... hang two or three side by side ... put some led strips inside to make it look like a lamp ... walmart.com/ip/…
    – jsotola
    Commented Jun 14, 2020 at 1:41
  • 1
    You might try something like a flex duct for a 6” range hood, it’s not very expensive but may help with your plan it is almost like heavy aluminum foil with a spiral wire a 1’ section turns into ~8 ‘, cold air is dense so it drops even a fan directly on or above the vent will really help by pushing the cold up and mixing the air this may be the biggest bang for the buck , circulating air also helps us to feel cooler as it moves the 98.6 degree heat away from our body so it is a win win with a fan mix the cool air by blowing up and the circulating air can help to cool.
    – Ed Beal
    Commented Jun 14, 2020 at 4:05

2 Answers 2


The easiest way to deal with this common issue is a vent booster fan, such as this example. It would not take up wall space nor be unsightly.

Without more information, such as the size of the vent opening or mains voltage, it would be impossible to be more specific. A photo of the room and a closeup of the vent might be helpful. Browse HVAC suppliers, online stores, etc.

  • Thank you for all the useful ideas! I have added a schematic diagram of the room. The register booster seems to be the easiest and most aesthetic solution. I did not even know they existed. Thank You. I just have to find one with a good CFM. Commented Jun 15, 2020 at 16:16

There ate many different types of pipes, tubes, and ducts that you could use, but there's also a furniture solution.

just use a folding room divider folded into a box shape. Seal around the base with draught-excluder saussages. if needed seal the seems with gaffer tape

If you're on an extreme budget you could use an empty refrigerator box.

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