So we are just under a year in our new home. We moved in back in March (on the tail end of cold season). It is two story, and like most two story homes, the conditioned air tends to stratify heavily before reaching equilibrium.

I was wondering if anyone had ever successfully rigged a circulation system that would operate a fan unit that pulls the hot air from the common area on the second floor and pushes it to the far corners of the first floor, essentially helping to mix the air and make it more uniform. It wouldn't need to be heated or cooled, so pushing it through the coils wouldn't be necessary. I guess it could be run in reverse in the summer to pull colder air from the first floor and push it upstairs, though the stratification is less noticeable in the summer.

I see it being run three ways:
1: integrated with the existing system, utilizing its duct work and somehow tied into the thermostats.
2: separate electronics but maybe using the existing ductwork via dampeners tied to shutoff switches (IF fan on AND damper open, RUN FAN, ELSE OFF).
3: completely separate electronics and completely separate ductwork.

Thoughts? Has anyone successfully retrofitted their home with something like this, and did it seem to make a difference?

move hot air from the second story common area to the peripheral of the first floor?

no, no it doesnt.

35chililights said:

---

move hot air from the second story common area to the peripheral of the first floor?

no, no it doesnt.

---

Ok, so ceiling fans in common rooms both up and downstairs.

Is that not what the fan function is for on your HVAC system?

Most two stories houses either have dedicated units for up and down stairs or are zoned, no?

I added return air registers for upstairs and downstairs units as high as I could on a wall in an upstairs game room right under the peak of the ceiling. So this was mixing inlet air from the highest point in the house to the inlet plenum of the unit that delivered conditioned air to the downstairs rooms.
To improve distribution in the house I always thought about converting some of the delivery ducts to return air ducts but never got around to it. I added a couple of return air registers and ducts to the upstairs unit and put larger inlet plenums on both units to accommodate the additional ducts.
This is a lot simpler than what you are thinking about but I think it had a positive impact.

BigNastyNate said:

---

Is that not what the fan function is for on your HVAC system?

Most two stories houses either have dedicated units for up and down stairs or are zoned, no?

---

That's what I was thinking. Just turn the fan from "auto" to "on" and it should accomplish the task of mixing the air.

the issue is that the upstairs and the downstairs are currently set up as two completely separate units. So the inlet for the upstairs unit is in the upstair's hallway. the inlet for the downstairs in in a hall on the first floor. So when the upstairs set point is 70, but the temperature is 76, the upstairs unit never runs. turning on the fan would only work to circulate the 78 degree are upstairs.

likewise, when the down stairs set point is 70, but the temperature is 68, the heater will run and we "loose" additional hot air to the upstairs further increasing the upstairs temperature. running the downstairs fan in this situation would only work to circulate the 68 degree air. it would not mingle with the upstairs 78 degree air.

when we finally kicked the heaters on this year, the difference was more noticeable. it was close to the example above. now that the house has somewhat equalized, the difference is only about 4-5 degrees. However, when we are going in and out of the house (or when the damned kids leave the door open) it moves the difference larger again.

this is happening mostly because of the floorplan. there is a high ceiling off the first floor that goes all the way up to the level of the ceiling of the second floor.

would it be possible to have the return air vent that feeds the first floor have a T-intersection allowing me to pick first floor or second floor? that seems to be the easiest solution to pull off, if that is indeed possible. that would allow me to run the 'fan' to circulate the warmer air back down to the first floor, as well as pull the already warmer air off the second floor when the furnace needs to run.

Probably not what you're looking for but my house has an HRV unit (Heat Recovery Ventilator). I'm up north and we don't have forced air. As a result of building tight houses we're prone to poor air quality in the winter when everything is shut trying to keep heat in. The HRV system will pull "bad air" out of my house and exchange it with and equal volume of fresh outside air. there is a heat exchanger that warms up the outside air near the inside air temperature.

The advantage for me is that I have some return registers high up on my vaulted living room ceiling that has lot's of hot air from our wood burning fireplace. It's heating up the outside air and pushing it into other rooms.

This is most likely too expensive and too late to install in your already built house. But I thought I'd offer it. I have a zehnder comfo air 550 and installed it myself while my house was in construction and just framed.

I had the same floorplan you describe. Look at my first response to your post.
3900 sq ft house. From just inside the front door entry you could look all the way up to the highest point of the second floor, the ceiling in the upstairs game room about 30 feet up. I added two return air registers to a wall just under the peak of the game room ceiling. It was most useful in the winter when those return air registers fed hot air to each furnace inlet. One fed the upstairs unit and the other fed the downstairs unit. In summer when it was really hot I put a piece of cardboard in the register to let the hot air stay above the living area.
The house is in Houston.

My home... 1977 build two story, single HVAC system with a return air in the stairwell. There is no grand two story common room. There is an attached, enclosed, and slightly climate controlled sunroom that has very high ceilings.

The sunroom stays cooler in the winter and a few degrees warmer in the summer, but it's not uncomfortable. I do want to add a second return air in the end of the upstairs hallway. I look into electric or even mechanical dampers so I can adjust where the air is pulled from seasonally. The upstairs stays much warmer in the summer months.

We have the same setup. We solve it by setting the thermostat on the upstairs to a higher temp. This allows the upstairs to run more appropriately.