most efficient way to heat/cool multi-unit house


Old 06-24-13, 04:25 PM
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most efficient way to heat/cool multi-unit house

I have a 3800 sq ft house with one unit controlling the main living floor and a walk out basement (all used). I have a separate smaller unit that controls the upstairs two bedrooms and bonus room (unused). I also have a whole house fan that I use when the temp drops below about 70. I also have insulation between all my floors. My basement is about 5-10 degrees cooler than my main living floor (thermostat is in the main living floor). How would I go about balancing the temp between the basement and the main floor? And should I do anything about cooling the upstairs unused rooms to prevent heat soak into the air conditioned space? I'm in Alabama, where 95+ degree days with high humidity aren't unusual. Thanks for any input!
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Old 06-24-13, 09:40 PM
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Welcome to the forums.

Your title is a little misleading. Your title makes it sound like you are looking for equipment but you have it and want to balance it.

I wouldn't run the upstairs air if the rooms weren't used but I'd make sure I had an automatic attic fan. I see you have a whole house fan which is good but you need to remove the heat from the attic and not draw air from the entire house.

I have an automatic fan in the roof and a whole house fan mounted to the gable end of the house. The auto fan runs most of the day to cool the attic. The makeup air for it is sized in eave vents. So when the auto fan runs it doesn't draw any air from the house. When the whole house fan is on I open a hallway door with a screened hatch to the attic.

As far as the first floor and the basement....that would have to be handled with registers you could shut in the basement during the summer.
Old 06-24-13, 10:03 PM
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run a vent tube from your ac unit to your furnace tubes.
Old 06-25-13, 05:06 AM
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I had to re-read the OP a second time to try and get a handle on things.

If you are running ducted AC as I understand it, for the basement, close a couple registers should help.
If you do not have registers that can close, look into magnetic register covers. I used these at my old house and this worked.
Old 06-25-13, 05:09 AM
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Can you get to the main trunk lines? There should be dampers on each line off the main trunk. Adjust those accordingly to balance the system. If there are no dampers on the main trunks, then close vents in the basement level to balance the system.
Old 06-25-13, 04:16 PM
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Sorry for the confusion on the title. All of the ducting is run in the space above a dropped ceiling in the basement so I should be able to get to the dampers.

I'll check into the attic fan. Sounds like what I need.
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