Higgy,

It all depends on your floor plan and where the small unit would do the most good. In my place, the top floor is just one long room. It has windows at each end wall of the house. I put my unit in the end where the stairwell comes out. When it runs, the cooler air fills up the stairwell first, then fills up the whole story with cooled air. It is set warmer than the central unit below, so it won't try to cool the whole house. It functions as a dehumidifier more than anything.

When the central unit downstairs kicks on, the dried return air from upstairs takes much less capacity to cool because the central unit doesn't have to condense liters of humidity. The central unit runs for less time each cycle and cycles less often. It saves energy because even though the upstairs window unit isn't as efficient, it's not cooling the air upstairs to the same lower temperature as the larger unit downstairs. I'm not trying to "freeze" the air upstairs.

This is kind of the opposite of the original idea of moving cool basement air to a higher level of the house. If you have a basement which occupies a large portion of the footprint of your house and can circulate this cooler air to the top story of your house efficiently, you would achieve a similar result for much less energy. However, Ryland found that his circulator fan consumed as much energy to run as a small window ac unit and did not dehumidify as well as he wished. As for me, I don't even have a basement...

I have a 2nd living room upstairs, so I have the window Air conditioner in that room, my brother puts his in the window in the upper hallway at the top of the stairs.
You release a lot of water while sleeping and bedding holds a lot of water making it uncomfortable so drying out your bed room makes sense to me, the idea is not to chill the house but instead to dry it out and dump the heat outside, I have to have the air conditioner run a lot longer if I want to chill the house, but if I set it to dehumidify then it drys the air pretty quick, making it feel cooler without being cold and without using a lot of energy because the greater the heat difference is between two areas the greater the losses.

Natures Airconditioner
 

I live in Upstate New York. Very hot and humid summers. I have a full renovated basement that stays a constant 54 degrees all year long. I have tried to fan the cool air upstairs (Ranch style Home). This works well on 80 degree days but on the hotter July and August humid days (90+) the upstairs temp climbs to 85+.

I have a forced hot air gas furnace with metal duct work and vents in each room on the main floor of my home with no fan only mode on the thermostadt.

So, I went to Home Depot, purchased a cheap energy star rated radon pump and 4" plastic pipe. Mounted the pump on my basement floor, in the bathroom near the incoming main house water supply line. (The coolest part of my basement)
I cut a hole in the ceiling and metal duct work, I installed a 4" vent ring used to mount on the roof for exhausting the radon out, and pumped that cool air in my duct work. Works like a constant A/C is on, cool air all the time, basement is less humid and all is good... P.S. Used a radon test kit first and have radon dector in place.

Terralore,

That's what I'm talking about! Can you elaborate on the strategy you use to operate the rig as well as your overall impression of comfort and bang for the buck the rig provides? There are many members that could benefit from such an upgrade, but many are pessimistic as to whether it's worth the effort and expense.

Great to hear its working out for someone. I must say I'm surprised to hear that your basement humidity hasn't increased though.

I used to think the same thing about my basement until I started to actually measure and record temperatures in the basement on a regular, periodic basis. That's when I came to realize that the basement temp actually did change. However, it was always a comfortable margin cooler than the rest of the house.

This is really a cheap straightforward hack. Way to go!

It would be useful for us all, if you kept a log of the upstairs temps and also the basement temps. A data logger would be nice, but a notebook with date & time & temps can go a long way.

Best,

-AC

Any updates on your setup Terralore?

It's been so hot, my basement temp is about 72 degrees. So not much help to be had from there.

My basement stays pretty cool all summer long. I don't think it ever gets above mid 50s... I'd like to try something like this.

New furnace!
Instead of the fan drawing 650 watts like the old one did, the new one has a low speed option that draws 70 watts, combine this with a single window AC unit at the top of the stairs in the 2nd floor of my house and the house is staying very comfortable!